System For Stimulating A Hypoglossal Nerve For Controlling The Position Of A Patient&#39;s Tongue

ABSTRACT

A system for controlling a position of a patient&#39;s tongue includes attaching at least one electrode to the patient&#39;s Hypoglossal nerve and applying an electric signal through the electrode to at least one targeted motor efferent located within the Hypoglossal nerve to stimulate at least one muscle of the tongue. The system may also include the use of more than one contact to target more than one motor efferent and stimulating more than one muscle. The stimulation load to maintain the position of the tongue may be shared by each muscle. The position of the patient&#39;s tongue may be controlled in order to prevent obstructive sleep apnea.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/779,938 filed Feb. 28, 2013, now U.S. Pat. No. 8,886,322, which is acontinuation of U.S. patent application Ser. No. 12/787,206 filed May25, 2010, now abandoned, which claims the benefit of U.S. ProvisionalPatent Application No. 61/259,893 filed Nov. 10, 2009 entitled “SystemFor Stimulating A Hypoglossal Nerve For Controlling The Position Of APatient's Tongue”, which is are hereby incorporated by reference intheir entirety.

BACKGROUND OF THE INVENTION

The present invention generally relates to a system for stimulating aHypoglossal nerve for controlling the position of a patient's tongue. Inone embodiment, the Hypoglossal nerve is stimulated to preventobstructive sleep apnea.

Sleep apnea is a sleep disorder characterized by pauses in breathingduring sleep. Those affected by sleep apnea stop breathing during sleepnumerous times during the night. There are two types of sleep apnea,generally described in medical literature as central and obstructivesleep apnea. Central sleep apnea is a failure of the nervous system toproduce proper signals for excitation of the muscles involved withrespiration. Obstructive sleep apnea (OSA) is caused by episodes ofphysical obstruction of the upper airway channel (UAW) during sleep. Thephysical obstruction is often caused by changes in the position of thetongue 110 during sleep that results in the closure of the soft tissuesat the rear of the throat or pharynx (See FIGS. 1, 2A and 2B).

OSA is characterized by the complete obstruction of the airway causingbreathing to cease completely (Apnea) or partially (Hypopnea). The humanairway (at the level of the thorax) is lined by soft tissue, anycollapse of its walls results in the closure of the airway which leadsto insufficient oxygen intake, thereby interrupting one's sleep(episodes or micro-arousals).

During sleep, the tongue muscles relax. In this relaxed state, thetongue may lack sufficient muscle tone to prevent the tongue fromchanging its normal tonic shape and position. When the base of thetongue and soft tissue of the upper airway collapse, the upper airwaychannel is blocked, causing an apnea event (FIG. 2B). Blockage of theupper airway prevents air from flowing into the lungs, creating adecrease in blood oxygen level, which in turn increases blood pressureand heart dilation. This causes a reflexive forced opening of the upperairway channel until normal patency is regained, followed by normalrespiration until the next apneaic event. These reflexive forcedopenings briefly arouse the patient from sleep.

OSA is a potentially life-threatening disease that often goesundiagnosed in most patients affected by sleep apnea. The severity ofsleep apnea is determined by dividing the number of episodes of apneasand hypopneas lasting ten seconds or more by the number of hours ofsleep. The resulting number is called the Apnea-Hypopnea Index, or AHI.The higher the index the more serious the condition. An index between 5and 10 is low, between 10 and 15 is mild to moderate, over 15 ismoderately severe, and anything over 30 indicates severe sleep apnea.

Current treatment options range from drug intervention, non-invasiveapproaches, to more invasive surgical procedures. In many of theseinstances, patient acceptance and therapy compliance is well belowdesired levels, rendering the current solutions ineffective as along-term solution.

Current treatment options for OSA have not been consistently effectivefor all patients. A standard method for treating OSA is ContinuousPositive Airway Pressure (CPAP) treatment, which requires the patient towear a mask through which air is blown into the nostrils and mouth tokeep the airway open. Patient compliance is poor due to discomfort andside effects such as sneezing, nasal discharge, dryness, skinirritation, claustrophobia, and panic attacks. A surgical procedurewhere rigid inserts are implanted in the soft palate to providestructural support is a more invasive treatment for mild to moderatecases of OSA. Alternate treatments are even more invasive and drastic,including uvulopalatopharyngoplasty and tracheostomy. However, surgicalor mechanical methods tend to be invasive or uncomfortable, are notalways effective, and many are not tolerated by the patient.

Nerve stimulation to control the position of the tongue is a promisingalternative to these forms of treatment. For example, pharyngealdilation via Hypoglossal nerve (XII) (FIG. 3) stimulation has been shownto be an effective treatment method for OSA. The nerves are stimulatedusing an implanted electrode to move the tongue and open the airwayduring sleep. In particular, the medial XII nerve branch (i.e., in.Genioglossus), has demonstrated significant reductions in UAW airflowresistance (i.e., increased pharyngeal caliber). While electricalstimulation of nerves has been experimentally shown to remove orameliorate certain conditions (e.g., obstructions in the UAW), currentimplementation methods typically require accurate detection of acondition (e.g., a muscular obstruction of the airway or chest wallexpansion), selective stimulation of a muscle or nerve, and a couplingof the detection and stimulation. These systems rely on detection ofbreathing and/or detection of apnea events as pre-conditions to controland deliver electrical stimulation in order to cause only useful tonguemotions and to periodically rest the tongue muscles and avoid fatigue.In one system, for example, a voltage controlled waveform source ismultiplexed to two cuff electrode contacts. A bio-signal amplifierconnected to the contacts controls stimulus based on breathing patterns.In another system, a microstimulator uses an implanted single-contactconstant current stimulator synchronized to breathing to maintain anopen airway. A third system uses an implantable pulse generator (IPG)with a single cuff electrode attached to the distal portion of theHypoglossal nerve, with stimulation timed to breathing. This last systemuses a lead attached to the chest wall to sense breathing motions bylooking at “bio-impedance” of the chest wall. Still another systemmonitors vagus nerve electroneurograms to detect an apnea event andstimulate the Hypoglossal nerve in response.

What is needed is a system and method of electrical stimulation of theHypoglossal nerve for controlling tongue position that is not tied tothe detection of breathing and/or an apnea event.

BRIEF SUMMARY OF THE INVENTION

A system for stimulating a Hypoglossal nerve for controlling theposition of a patient's tongue according to some embodiments of thepresent invention includes an electrode configured to apply one of atleast one electric signal to one of at least one targeted motor efferentlocated within a Hypoglossal nerve to stimulate at least one muscle ofthe tongue.

In a further embodiment, the system further includes an implantablepulse generator (IPG) coupled to the electrode. In a further embodimentthe system includes a remote control and charger coupled to the IPG. Inone embodiment the remote control powers the IPG. In a furtherembodiment, the remote control re-charges the IPG. In a furtherembodiment, the system includes a docking station configured to chargethe remote control and charger. In one embodiment, the remote controland charger are configured to couple with a computer to program the IPG.In a further embodiment, the system includes a sensor configured tomeasure the temperature of the IPG. In one embodiment, the electrodeincludes a plurality of contacts. In one embodiment, the IPG isprogrammable to assign the contacts to one of a plurality of functionalgroups. In one embodiment, the IPG is programmable to sequence orinterleave the functional groups. In one embodiment, each functionalgroup maintains an open airway in the patient and a first functionalgroup includes at least one or more different muscles than a secondfunctional group. In one embodiment, the electrode includes sixcontacts. In one embodiment, the contacts are each driven by their ownindependent current source.

In a further embodiment, the system includes a Medical ImplantCommunication Service (MICS) telemetry transceiver. In a furtherembodiment, the system includes an inductive link telemetry transceiver.In a further embodiment, the system includes a primary boot loader. In afurther embodiment, the system includes a secondary boot loader. In oneembodiment, the electrode includes a cuff housing configured to wraparound a portion of the Hypoglossal nerve. In one embodiment, theelectric signal is applied to the Hypoglossal nerve via an open loopsystem. In one embodiment, the electrode is driven by multiple currentsources. In a further embodiment, the system includes event loggingmemory. In a further embodiment, the system includes a multiplexerconfigured to measure impedance of at least one of the electrodecontacts and patient tissue. In one embodiment, the IPG is covered by ahermetic enclosure.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The foregoing summary, as well as the following detailed description ofexemplary embodiments of a system for stimulating a Hypoglossal nervefor controlling a position of a patient's tongue, will be betterunderstood when read in conjunction with the appended drawings. Itshould be understood, however, that the invention is not limited to theprecise arrangements and instrumentalities shown.

In the drawings:

FIG. 1 is an illustration of the human airway;

FIG. 2A is an illustration of an open human airway;

FIG. 2B is an illustration of a closed human airway during an apneaevent;

FIG. 3 is an illustration of the human tongue;

FIG. 4A is an illustration of a cross-section of a human Hypoglossalnerve;

FIG. 4B is an illustration of a cross-section of a human Lingual nerve;

FIG. 4C is an illustration of a cross-section of a rat Hypoglossalnerve;

FIG. 5 is an exemplary set of fatigue curves of human quadriceps muscleshowing maximum voluntary contraction, 50 Hz electrical stimulation andtwitch responses;

FIG. 6 is an exemplary illustration of an electrode attached to apatient's Hypoglossal nerve;

FIG. 7 is a perspective view of the electrode;

FIG. 8 is a perspective view of the electrode showing the plurality ofcontacts;

FIG. 9 is a graphical representation of an exemplary stimulationstrategy;

FIG. 10A is a graphical representation of an exemplary duty cyclestimulation strategy;

FIG. 10B is a graphical representation of an exemplary interleavedstimulation strategy;

FIG. 10C is a graphical representation of an exemplary synchronousstimulation strategy;

FIG. 10D is a graphical representation of an exemplary asynchronous orrandom stimulation strategy;

FIG. 11 is an exemplary strength-duration curve;

FIG. 12 is a block diagram of the IPG;

FIG. 13 is a partially exploded perspective view of the IPG with itsheader and inline connector attachment to the enclosure andfeedthroughs;

FIG. 14 is a perspective view of the battery support for the IPG;

FIG. 15 is a partial perspective view of the IPG electronics assemblybeing inserted into its titanium enclosure;

FIG. 16 is an exploded perspective view of the IPG and the siliconeheader components, the connector components which attach to thefeedthroughs, the guides for the connectors, the inductive chargingcoil, the antenna coil, the magnet and the inline connector assemblywith strain relief;

FIG. 17 is a schematic diagram of the IPG Power Sections;

FIG. 18A is a first schematic diagram section of the IPG MicrocontrollerSection and Log Memory;

FIG. 18B is a second schematic diagram section of the IPGMicrocontroller Section and Log Memory;

FIG. 19 is a schematic diagram of the IPG Pulse Generation and AnalogSignal Sampling Circuits;

FIG. 20 is a schematic diagram of the IPG Medical Implant CommunicationsService (MICS) Telemetry Section;

FIG. 21 is a schematic diagram of the IPG board to board connections andManufacturing Test Adapter;

FIG. 22 is a diagram of the Remote Control and Charger (RCC) Front PanelKeyboard and LEDs;

FIG. 23 is a block diagram of the RCC;

FIG. 24 is a schematic diagram of the RCC Docking Station and UniversalSerial Bus (USB) Interface Sections;

FIG. 25 is a schematic diagram o the RCC Power Sections;

FIG. 26A is a first schematic diagram section of the RCC MicrocontrollerSection;

FIG. 26B is a second schematic diagram section of the RCCMicrocontroller Section;

FIG. 27 is a schematic diagram of the RCC MICS Telemetry Section;

FIG. 28 is a schematic diagram of the RCC Keyboard and LED Sections;

FIG. 29 is a block diagram of the Charger Coil (CC);

FIG. 30 is a depiction of the aura Clinical Manager (aCM) PatientManager Screen;

FIG. 31 is a depiction of the aCM Titration Screen;

FIG. 32 is a depiction of the aCM RCC Functions Screen;

FIG. 33 is a depiction of the aCM Manual Parameter Control Screen;

FIG. 34 is a depiction of the aCM RCC USB Comm Screen;

FIG. 35 is a block diagram of the Implantation Use Model;

FIG. 36 is a block diagram of the Titration Phase Use Model;

FIG. 37 is a block diagram of the Patient Use Model;

FIG. 38 is a flow diagram for the On/Off Key of the RCC

FIG. 39 is a flow diagram for the Charge Key of the RCC;

FIG. 40 is a flow diagram for the Test Key of the RCC;

FIG. 41 is a flow diagram for the Pause Key of the RCC;

FIG. 42 is a flow diagram for the IPG Pause Process;

FIG. 43 is a flow diagram for the IPG Charge Process;

FIG. 44 is a flow diagram for the Sleep Process;

FIG. 45 is a flow diagram for the Frequency Tick Process;

FIG. 46 is a flow diagram for the Next Group Delay Tick Process;

FIG. 47 is a flow diagram for the Sleep Duration Tick Process;

FIG. 48 is a flow diagram for the Group On Time Tick Process;

FIG. 49 is a flow diagram for the Impedance Measurement Process;

FIG. 50 is a flow diagram for the secondary Boot Loader Process;

FIG. 51 is a flow diagram for the IPG Main Application Process;

FIG. 52 is an exemplary representation of a stimulation strategy withtwo active groups;

FIG. 53 is an exemplary representation of alternative embodiments of thesystem elements;

FIG. 54 depicts an alternative embodiment of a Remote Control;

FIG. 55 depicts keyfob telemetry relays;

FIG. 56 depicts an alternative embodiment of a Charger and Charger Coil;

FIG. 57 depicts an alternative use model for the Clinician;

FIG. 58 depicts an another alternative use model for the Clinician;

FIG. 59 depicts a use model for the patient;

FIG. 60 depicts another use model for the patient;

FIG. 61 depicts a use model for the patient when charging the IPG; and

FIG. 62 depicts another use model for the patient when charging the IPG.

DETAILED DESCRIPTION OF THE INVENTION

Similar to the embodiments described in U.S. patent application Ser. No.12/572,758, which is hereby incorporated by reference in its entirety,the system described herein operates in an open-loop continuous fashionto stimulate the hypoglossal nerve (HGN) of a patient suffering fromOSA. Referring to FIG. 3, the Hypoglossal Nerve (HGN) 322 is primarily amotor nerve and activates the various extrinsic and intrinsic muscles ofthe tongue. The tongue 110 has been described as a hydrostat, a musclethat is constrained within a relatively fixed volume, without thebenefit of generating forces between two bony surfaces. Much like thetrunk of an elephant, the tongue is able to change its shape by thecontraction of its various muscle elements to protrude and retrude thetongue, curl, flatten, move up or down within the oral-pharyngeal cavityto assist with breathing, speech, mastication and swallowing.

The tongue muscle is different from other muscles in the body in that ithas been demonstrated to have unique fatigue resistant properties. Thetongue can be artificially activated by electrical stimulation for longperiods of time without the typical position or force degradation thatis accompanied with skeletal muscle when it is electrically stimulated.Like the heart, gastro-intestinal, and a few other specialized muscleswithin the human body, the tongue muscles have properties that make themparticularly attractive for nearly constant activation, and thus the HGN322 is amenable to the methods described here to maintain muscle toneand hence position and shape during sleep that are normally presentduring wakeful hours for the patient but are absent during the deepestlevels of sleep.

As is known in the art, excitation of a nerve fiber can occur along astrength duration iso-threshold curve, a nerve fiber will be excited aslong as the amplitude is above the curve or the phase duration is to theright of the curve. An exemplary strength curve is shown in FIG. 11. Ateither end of the curve the shape of the curve is asymptotic; at alimiting phase duration no amount of stimulation current elicits aresponse, and at the other no phase duration is long enough to elicit aresponse either. The invention described herein may refer to the use ofstimulus amplitude for means of modulating the recruitment of nervefibers, but it shall be understood that many methods, including phaseduration and stimulus amplitude, can be utilized to the same ends ofactivating nerve fibers with electrical stimulation.

Nerve fibers are preferentially activated, or recruited, in the order oftheir proximity to the electrode contact and by their fiber diameter. Asa general rule, the closer a fiber is to the cathodic contact, the morelikely it will be activated (the general form of a stimulating system isto place the cathodic contact in close proximity to the target nerveaxons; other forms of stimulation exist and shall be obvious to thoseskilled in the art). The larger the diameter of a fiber, the more likelyit will be activated. The distance and size distribution in a nervebundle does not change appreciably over time. Hence, the recruitmentproperties—which fibers will be activated with a particular amplitudepulse—do not change either. If the applied stimulus is maintained at asufficiently high enough frequency, the recruited muscle fibersactivated by the stimulated nerve fibers eventually fatigue. Muscleforce and/or position then changes towards the relaxed, inactivatedcondition. The stimulation of skeletal muscle for postural control orlimb motion is often performed at frequencies that would normally beexpected to cause fatigue in those muscles along with the loss ofdesired function if the stimulation were maintained continuously.Stimulation may be modulated by changing the stimulus amplitude, asdescribed above, or by changing the phase duration of the pulse. Greatcare and tremendous effort are expended in avoidance of fatigue inskeletal muscle applications for fear of loss of desired functionaleffect, for example, for patients suffering from spinal cord injury orother neurological dysfunction.

Peripheral nerves such as the HGN 322 are organized often by groupingfibers that go to each of the branches at the distal end of the nerveinto fascicles, or tubules within the main nerve bundle. Cross sectionsviews of such peripheral nerves clearly show this organization asseparate regions of nerve fibers. Stimulation electrodes placed closedto these bundles or fascicles preferentially activate the fibers goingto the down-stream muscle groups. FIGS. 4A, 4B and 4C demonstrate theorganization structure of the Human Hypoglossal nerve 322 (FIG. 4A) andthe Human Lingual Nerve (FIG. 4B), as well as the Rat Hypoglossal Nerve(FIG. 4C). The Hypoglossal nerves in both Human and Rat are afascicular,lacking the clear organizational structure present in most peripheralnerves, and which is present in the Human Lingual Nerve, as described inU.S. patent application Ser. No. 12/572,758, hereby incorporated byreference in its entirety. Nonetheless, it is organized and electrodesplaced around the circumference can be used to target specific nervefibers and hence muscle groups to affect only desirable musclefunctions, movements, and motions.

Fatigue may be minimized or prevented by using a stimulation dutycycle—that is, stimulating for a certain amount of time beforesignificant fatigue sets in, then stopping to let the muscle rest andregain its ability to contract. For obstructive sleep apnea this is lessthan optimal because without an applied stimulus during the off periodof the electrical stimulation duty cycle the tongue would not be drivento maintain a desired position, and could fall back against the rear ofthe throat and allow an apnea event to occur. This is one of the reasonsthat many OSA stimulation systems rely on sensors to detect when toapply stimulation and when to leave it off. The method of using dutycycle to rhythmically apply stimulation has been proposed, also, to doaway with the need to sense breathing events, in the hopes that byintroducing rhythmic stimulation to the Hypoglossal nerve that somehowthe breathing events would synchronize automatically to the stimulationtiming. This has not been proven and studies, which usedmicrostimulators in sheep, demonstrated that manual timing ofstimulation to the events of breathing was required to achieve a usefuloutcome in single point stimulation of the Hypoglossal nerve.

Another method of minimizing or preventing muscle fatigue is to use oneor more independent current sources to activate multiple portions of thedesired muscle groups. In certain exemplary embodiments, one or moreindependent current sources drive one or more contacts (764 a, 764 b,764 c and 764 d for example shown in FIGS. 7 and 8) that interface withthe Hypoglossal nerve 322. These contacts are optionally contained in asingle cuff electrode 764 as shown in FIGS. 7 and 8. Each contact can beactivated separately or in combination with other contacts as discussedfurther below.

In certain embodiments, each contact is assigned to one or morefunctional or muscle groups. Functional groups may in turn be used toselect regions of fibers within the nerve bundle that result in adesired tongue movement. The effort of moving the tongue to the desiredposition is thus shifted from one functional group to another functionalgroup so that no single functional group is required to work all of thetime. Thus, the effort of moving the tongue is shared among multiplestimulated nerve fibers and their associated muscles, preventing orreducing fatigue because none of the groups are activated long enough tocause significant fatigue, and during their off, or non-stimulated,state they are allowed to recover from the stimulation. In certainexemplary embodiments, each group is active until just beforesignificant fatigue sets in. One or more additional groups are thenactivated to take its place, allowing the former muscle group fibers torest. In one embodiment, the stimulation is spread over more than onecontact wherein the duty cycle of each contact is overlapped (FIG. 9).

A more detailed depiction of this transfer of muscle work load from onegroup to the next is depicted in FIG. 52. The course of events thatoccurs from the time that the patient starts a sleep session through thefirst group stimulation cycle and the beginning of the next is shown.After the initiation of a sleep session, a delay occurs allowing thepatient to fall asleep. After the delay, the first group begins tostimulate, using its threshold amplitude, slowly ramping up for theduration of the ramp, until at the conclusion of the ramp and thebeginning of the plateau phase the stimulation current amplitude hasreached its target level. This ramp may help to prevent the patient frombeing aroused from sleep by the sudden start of stimulation at thetarget level. At the time that the ramp up began, the delay to the nextgroup start was started as well, to allow the coordination from onegroup to another. After the plateau duration is complete for the firstgroup, the stimulation begins to ramp back down to threshold for theramp down duration. At the conclusion of the ramp down duration, thegroup is deactivated and the second group should already have begun itsstimulation cycle. At the conclusion of the next group delay, the nextgroup begins its stimulation cycle and the group after that begins itsdelay. All the while that stimulation is being ramped in the first andeven perhaps in the second groups, frequency is being ramped down from astarting frequency to a target frequency after which the frequencyremains at the target level until the end of the sleep therapy. Thisallows the smooth transition from one stimulation group to the next, andby ramping frequency downwards to the target frequency providesadditional opportunity to prevent arousal and promote the comfort of thestimulation sensation to the patient.

In one embodiment, the stimulation pulses may be generally random orpseudo random so long as the overall contractions per unit of time islimited (see FIG. 10D).

Another method of reducing or eliminating fatigue is to lower thestimulation frequency. The faster a nerve is stimulated, the faster itfatigues. Each pulse produces a contraction, with each contractionrequiring a certain amount of work. The more contractions there are, themore the muscle works, and the more likely the muscle will becomefatigued. Reducing the stimulation frequency to a rate just fast enoughto achieve the desired response minimizes the rate at which musclecontractions occur. This minimizes the amount of work done by themuscle, delaying or minimizing muscle fatigue. In one embodiment, thestimulation is spread over more than one contact wherein each contactdelivers a generally equal fraction of stimulation frequency that is outof phase with the other contacts (FIG. 10B). This method reduces thestimulation rate for each of the independent groups but results in afunctional stimulation rate that is essentially the sum of the ratesthat are active. As shown in FIGS. 10A and 10B, the same effective forceor position is maintained, but in FIG. 10A fatigue is prevented by dutycycle method and in FIG. 10B it is prevented by three groups running atone third the frequency of any one group in FIG. 10A resulting in thesame muscle force or position and the same prevention of fatigue.Stimulation frequencies that have been used for activating skeletalmuscle have often required the use of a frequency that results intetanus, a smooth fusion of pulses fast enough to maintain a nearcontinuous level of force or position. Tetanus is not required, per se,in the artificial activation of the tongue—the patient is asleep, andthe cosmetic appearance of the tongue while it is activated is notnearly as important as the maintenance of airway patency. Experimentalevidence has shown that stimulating at frequencies below 5 pulses persecond have been adequate to maintain airway patency in patients withsevere OSA.

Continuous or near continuous stimulation of a muscle is discouraged inthe art because of fatigue problems. However, in view of the teachingherein, the tongue 110 is a fatigue resistant muscle. Testing in bothrats and humans has confirmed this finding. In limited animal studies,it was demonstrated that rat tongue muscle could be stimulated at veryhigh frequencies for extended periods without observable changes intongue position. In one study, rather than stimulating at 15 pulses persecond (pps), a frequency adequate to move the tongue sufficiently toclear the rear of the throat, stimulation was applied at supra-thresholdlevels at a frequency of 100 pps. The resulting tongue response wasmaintained for more than one hour before any significant change intongue position could be detected. If the stimulation frequency weredropped to 15 pps, it is likely that stimulation may be applied morethan five times longer before tongue position change would be expectedto occur. In human trials, embodiments disclosed herein successfullystimulated patients with a fixed set of electrode contacts for manyhours before the anti-apnea effect was seen to diminish. In oneembodiment, using lower frequencies and multiple contacts on a humantongue increases the duration that stimulation could be applied beforeanti-apnea effects diminish.

Thus, with the tongue and associated rear throat tissues consistentlydriven in such a manner as to clear the airway there is no need todetect apneas because they simply will not be allowed to occur. Ratherthan timing stimulation to breathing, or monitoring for an apnea eventprior to initiating treatment, the exemplary embodiments stimulate theHypoglossal nerve in a predetermined manner via an open loop system toactivate targeted muscles in the tongue to maintain airway patency. Withairway resistance decreased and/or the tongue prevented from fallingback against the rear of the throat, and/or pharyngeal compliancereduced, there is no need to monitor for apneas, because they areprevented from occurring, nor monitor for ventilation timing because thestimulation is not timed or synchronized to breathing at all, it ismaintained continuously during the entire sleeping period.

The activation of a protrusor that moves the tongue forward and awayfrom the oral-pharyngeal junction, or the activation of a retrusor thatacts to decrease the compliance of the pharyngeal wall are bothdesirable in preventing the occlusion of the airway. Co-activation ofagonistic and antagonistic muscles has been shown in the literature toincrease stiffness and to maintain position of a joint or body segment,likewise, co-activation of protrusors and retrusors of the tongue shouldhave the effect of maintaining position and stiffness of the tongue andpharanygeal walls to a desirable effect. The activation of intrinsicmuscles that change the shape of the tongue may also lead to desirablemotions even though the actions of these muscles may not be clearlydefined in terms of protrusor or retrusor. It shall be understood thatthe activation of any tongue muscle that achieves beneficial motions oractions of the tongue musculature is a potential target of the selectivetargeted methods of electrical stimulation as described by the methodsof this patent and it shall not be the single object of the describedmethod to only activate protrusors per se.

Since the tongue is a fatigue-resistant muscle, it can be stimulated,using the techniques described herein, for long durations without lossof force or movement. By stimulating the Hypoglossal nerve, tongueactivation resembling normal daytime tongue muscle tone is restored tokey muscles during sleep. The tongue does not fall into the throat,keeping the airway open and allowing the patient to breathe normallyduring sleep. Continuous or near-continuous stimulation maintains thetongue in a desired position, shaping the airway, without the necessityof a complicated closed loop stimulation strategy with the associateddependence upon sensors and their interpretation. While the tonguemusculature is fatigue resistant, it is still susceptible to fatigue ingeneral. Therefore methods employed herein are still directed atmaintaining therapeutic effect by utilization of multiple groups tomaintain desired function and other methods such as frequency control tominimize the work load of any single muscle group.

Neurostimulation is often performed on peripheral motor nerves.Peripheral motor nerves emanate from the ventral horns of the spinalcord and travel in bundles to various muscle groups. A single motornerve bundle may contain many sub-groups of neurons. Some neuronsub-groups are organized into separate sub-bundles called fascicles,which are easily viewed in histological cross section, and often connectto groups of muscle fibers within the same muscle. With thesesub-groups, stimulation of the sub-group typically results in activationof a group of muscles working together to achieve a desired effect.

Other peripheral nerves, such as the Hypoglossal nerve, have sub-bundlesthat are not organized into fascicles. Instead, these sub-bundles run insomewhat controlled but less well defined regions of the nerve, and arenot easily recognizable in a cross-sectional view. These sub-groupsoften go to multiple muscle groups in different locations. An example ofsuch a nerve is the Hypoglossal nerve, which has multiple sub-groupsconnecting to different portions of the tongue. A more detaileddescription of the nerve structure for the human tongue is disclosed inU.S. Patent Application No. 61/136,102, filed Oct. 9, 2008, herebyincorporated by reference in its entirety.

Not every muscle of the human tongue is involved in the opening of theairway. Some stimulated muscles act to block the airway. In theembodiments described, the only nerves targeted by the targetedselective electrical stimulation method described herein are nerves thatstimulate muscles that activate the tongue resulting in the optimalopening of the airway and suppression of unwanted tongue movements. Incontrast, whole nerve stimulation activates the entire nerve contentsand nerve bundles containing nerve fibers to both desirable andnon-desirable groups of contracting muscles are simultaneouslyactivated. This not only leads to suboptimal levels of opening, but mayalso produce undesirable tongue motions. A surgical way to avoid thisproblem with less than optimal stimulation methods is to placestimulating electrodes on distal branches of the nerve that onlyinnervate the desired muscle groups, a task that is difficult andpotentially hazardous to the nerve.

In these cases, activation of the entire bundle from an artificialelectrical stimulus results in activation of all of the musclesactivated by the sub-groups within the stimulated nerve group. In thepresent invention, to target only the desired specific groups of fiberswithin a nerve bundle, exemplary embodiments use multiple nerveelectrode contacts and multiple independent controlled current sourcesto activate only the desired sub-groups. This minimizes or eliminatesthe likelihood of delivering stimulation to muscles not providing thedesired tongue position.

The Hypoglossal nerve in the region just below the sub-mandibular gland(proximal to the Styloglossus/Hyoglossus branches and distal to the ansacervicalis branch) is non-fascicular, that is, the various nerve groupsthat separate distally are not isolated in the bundle as fascicles, butare present en masse with all of the fibers of the Hypoglossal nerve. Asdescribed in the rat dye studies discussed in U.S. patent applicationSer. No. 12/572,758, and in studies on human cadavers, there appears,however, to be an organization to the bundle, with fibers mostlyinnervating the Genioglossus muscle residing in the medial region of thebundle. Studies conducted in rats, an animal model identified thus farthat replicates the non-fascicular nature of the human Hypoglossalnerve, revealed an organization of the whole nerve, suggesting thattargeted activation of a sub-population of neurons in the Hypoglossalnerve would be possible. Stimulation studies in rats and humans withmultipolar electrodes and multiple independent current sources verifiedthis with the result that multiple distinct motions and positions of thetongue could be achieved using targeted stimulation methods and devices.Placement of electrode contacts about the perimeter of the Hypoglossalnerve at this region has achieved targeted selective activation of thetongue muscles. The resulting airway changes elicited by stimulationdepend upon which electrode contacts are activated.

In one exemplary system, an electrode 764 is implanted around theHypoglossal nerve at or near an approximately 1 cm length of 2.5 to 4.5mm diameter nerve bundles. This is typically at the rear of and belowthe mandible, just underneath the sub-mandibular gland, proximal to theStyloglossus/Hyoglossus branches and distal to the ansa cervicalisbranch. At this point, the major branches to the various tongue musclesare distal to the electrode site.

Targeted Selective Stimulation of Hypoglossal Nerve Efferents

In one embodiment, the present invention is directed to the targetedselective stimulation of Hypoglossal nerve efferents in animals. In oneembodiment, the present invention is directed to the targeted selectivestimulation of Hypoglossal nerve efferents in mammals. In oneembodiment, the present invention is directed to the targeted selectivestimulation of Hypoglossal nerve efferents in rats. In one embodiment,the present invention is directed to the targeted selective stimulationof Hypoglossal nerve efferents in humans.

In one embodiment, the present invention is directed to the targetedselective stimulation of Hypoglossal nerve efferents via electricsignals emitted from at least one programmable electrode contact. In oneembodiment, the targeted selective stimulation of Hypoglossal nerveefferents occurs via multiple electrode contacts. In one embodiment, thetargeted selective stimulation of Hypoglossal nerve efferents is drivenby multiple current sources. In one embodiment, the multiple electrodecontacts are each driven by their own independent current source.

In one embodiment, the multiple electrode contacts each activate abeneficial muscle group and alternate in their operation such that thebeneficial function is maintained by at least one group at all times. Inone embodiment, the multiple electrode contacts each activate abeneficial muscle group and interleave their operation such that thepatency of the airway is maintained. In one embodiment, the multipleelectrode contacts each activate a beneficial muscle, and alternate intheir operation such that the patency of the airway is maintained. Inone embodiment, the multiple electrode contacts each activate one of abeneficial muscle, and interleave their operation such that the patencyof the airway is maintained.

In one embodiment, the method includes activating the ipsilateralGeniohyoid muscle. In one embodiment, the method includes activatingrostral or caudal or both compartments of the ipsilateral Geniohyoidmuscle. In one embodiment, the method includes activating at least onecompartment or both compartments of ipsilateral or with the rostralcompartment of the contralateral Geniohyoid muscles increasing thedilation (of the pharyngeal airway) and the patency of the airwaychannel.

In one embodiment, the modulating electric signals have a frequencysufficient for a smooth tetanic contraction. In one embodiment, themodulating electric signals have a stimulation frequency of about 10 toabout 40 pps. In one embodiment, the modulating electric signals are ofan intensity from about 10 to about 3000 microamps (μA). In oneembodiment, the modulating electric signals have a stimulation pulsewidth of about 10 to about 1000 microseconds (μs).

In one embodiment, the targeted selective stimulation of Hypoglossalnerve efferents activates at least one lingual muscle. In oneembodiment, the targeted selective stimulation of Hypoglossal nerveefferents activates at least one upper airway channel dilator muscle. Inone embodiment, at least one protrusor muscle is activated. In oneembodiment, at least one protrusor muscle and at least one retrusormuscle are alternately activated. In one embodiment, at least oneprotrusor muscle and at least one retrusor muscle are co-activated. Inone embodiment, the at least one protrusor muscle 400 activated is thegenioglossus muscle. In one embodiment, at least one beneficial musclegroup is activated. In one embodiment, at least two beneficial musclegroups are activated.

Method of Treating a Neurological Disorder Including Obstructive SleepApnea

In one embodiment, the present invention is directed to a method oftreating, controlling, or preventing a neurological disorder byattaching at least one programmable electrode to a patient's Hypoglossalnerve proper 322; and selectively applying electric signals to motorefferents located within the Hypoglossal nerve proper 322 through theprogrammable electrode 764 to selectively stimulate at least one muscle.In one embodiment, the electric signals are modulating. In oneembodiment, the method of treating, controlling, or preventing aneurological disorder consists essentially of the recruitment ofretrusor motor efferents. In one embodiment, the method comprises therecruitment of protrusor motor efferents. In one embodiment, the methodcomprises the recruitment of a ratio of retrusor to protrusor motorefferents such as the ratios described above to treat a neurologicaldisorder.

In one embodiment, the neurological disorder suitable for treatment,control, or prevention by the present invention is selected from thegroup consisting of, but not limited to oral myofunctional disorders,atrophies, weakness, tremors, fasciculations, and myositis. In oneembodiment, the neurological disorder is obstructive sleep apnea. Otherpotential applications of this method, in addition to treatment ofobstructive sleep apnea, include, for example, supplemental nervestimulation to keep the airway open for treatment of snoring, hypopnea,or countering motor activation of the tongue during a seizure. Otherhealth problems related to the patency of a patient's airway may also betreated using methods provided by the present invention.

In one embodiment, the present invention provides a method of treating,controlling, or preventing obstructive sleep apnea including the stepsof attaching at least one programmable electrode to a patient'sHypoglossal nerve proper 322; and selectively applying electric signalsto motor efferents located within the patient's Hypoglossal nerve proper322 through the programmable electrode 764 to selectively stimulate atleast one muscle. In one embodiment, at least one programmable electrode764 provides a continuous, low level electrical stimulation to specificmotor efferents to maintain the stiffness of the upper airway channelthroughout the respiratory cycle. In one embodiment, at least oneprogrammable electrode provides intermittent electrical stimulation tospecific motor efferents at controlled, predetermined intervalssufficiently close to achieve a constantly opened airway.

In one embodiment, the method of treating, controlling, or preventingobstructive sleep apnea includes selectively activating one or moremuscles in the upper airway channel to effectively reduce the severityof obstructive sleep apnea and improve airway patency. In oneembodiment, the method includes targeted selective stimulation of motorefferents that activate the geniohyoid muscle, causing anterosuperiormovement of the hyoid bone to increase the patency of the upper airwaychannel. In one embodiment, the method includes targeted selectivestimulation of functionally opposite muscles that also effectivelystiffen the upper airway channel to reduce the risk of collapse.

In one embodiment, the method of treating, controlling, or preventingobstructive sleep apnea consists essentially of the recruitment ofprotrusor motor efferents. In one embodiment, the method includesactivating at least one protrusor muscle. In one embodiment, the methodincludes targeted selective stimulation of protrusor motor efferentslocated within the Hypoglossal nerve proper 322 that activate thegenioglossus muscle, causing protrusion of the tongue to increase thepatency of the upper airway channel.

Elements of the System

In one embodiment, the OSA system is comprised of implanted and externalelements which together act to provide continuous open loop targetedselective stimulation of the HGN 322. The implanted elements (i.e. theelements implanted into the patient) may include an Implantable PulseGenerator 1370 (IPG) (see FIGS. 13-16) and a cuff electrode 764 (seeFIG. 7). The external elements may include a Remote Control and Charger2272 (RCC) (see FIG. 22), a Charger Coil 5374 (CC) and cable 5374 a, aDocking Station 5378 (DS) and a power supply for the patient, and anotebook computer 5376 and the aura Clinical Manager (aCM) clinician'ssoftware programming system. The IPG 1370 may be responsible forgenerating the pulses that activate the desired neurons within the HGN322, and is implanted in the anterior chest region of the patient. Thecuff electrode 764 may attach to the IPG 1370 via an inline connector,and runs from the chest location of the IPG 1370 to the sub-mandibularregion where it is wrapped around the HGN 322. The IPG 1370 may containa plurality, such as six, independent current sources, each capacitivelycoupled via feedthroughs in its enclosure to the inline connector. Theinline connector may have six torroidal spring contacts which mate withring contacts of the cuff electrode 764 proximal connector. Each ringcontact of the cuff electrode 764 may be connected by a wire in the cuffelectrode 764 assembly to a contact within the self-sizing cuff. Eachcontact may be shaped to match the curvature of the nerve bundle of theHGN 322, and the six contacts are located within the cuff so that sixsectors of the nerve circumference are in intimate contact with the cuffcontacts. The IPG 1370 may be directed by the RCC 2272 to start and stopa sleep therapy treatment session, to provide information on the statusof the IPG 1370 and the cuff electrode 764, and is used in conjunctionwith the CC to replenish the energy within the IPG 1370 battery. The aCMmay be used by a clinical engineer or clinician to program the OSAsystem for use in providing therapy to the patient.

Implanted Pulse Generator (IPG)

The Implantable Pulse Generator 1370 (IPG) for the OSA system is shownin FIG. 13. The IPG 1370 may be housed in a titanium enclosure,containing the secondary Lithium-Ion battery, the printed circuit board(PCB) assemblies, radio-opaque marker, and support structures. The IPG1370 may be covered by a hermetic enclosure. The titanium material maybe consistent with metals traditionally used to house Active ImplantedMedical Devices (AIMD). The top of the titanium case may be sealed witha titanium plate through which two feedthrough assemblies are attached.One feedthrough assembly may contain four feedthrough pins, two of whichmay be used for an inductive charging coil located outside the hermeticenclosure and inside the header assembly, and two of which may be usedfor the Medical Implant Communications Service (MICS) telemetry coilsimilarly located. The second feedthrough assembly may contain sixfeedthrough pins, which may be connected to output pulse circuitry ofthe IPG 1370 and which connect eventually to the six contacts containedwithin the cuff electrode 764 that attaches to the HGN 322. Anembodiment of the IPG assembly 1370 is shown in FIG. 13 showing thesilicone header and inline connector separated from the IPG 1370housing. FIG. 14 depicts the plastic battery support that protects theLithium Ion battery inside the IPG 1370 enclosure. FIG. 15 depicts thecompleted IPG internal assembly with circuit boards fastened to thetitanium header plate, the battery support and feedthrough assembliesbeing lowered into the titanium enclosure and completed by laser weldingthe enclosure to the titanium header plate. FIG. 16 shows an explodedview of the header elements, including the inductive link charging coil,the MICS telemetry coil, the magnet, the silicone inner and outer headerelements, the crimp contacts which mate with the feedthrough pins, thePolyetheretherketone (PEEK) guides, and the inline connector assemblyand strain relief. An alternative to this structure would utilize anepoxy header with the elements of the inline connector contained withinthe volume of the epoxy header, eliminating the PEEK components, crimpcontacts and allowing the proximal connector of the electrode lead to beinserted directly into the IPG epoxy header.

The IPG 1370 elements shown in the block diagram in FIG. 12 may consistof a 16 bit microcontroller, a MICS telemetry transceiver, a six channelcustom Application Specific Integrated Circuit (ASIC) current source, aserial electrically erasable programmable read only memory (SEEPROM),inductive power receiving and modulating and demodulating circuitry,battery charging circuitry, power supplies and analog signal acquisitionsupport circuitry. The microcontroller may have a large number ofresources, including a 16 bit reduced instruction set core (RISC), 92KBytes of Flash memory, 8 KBytes of RAM, a three channel DMA, a 12 bitanalog to digital converter (A/D) and digital to analog converter (D/A),16 bit timers with 10 capture and compare registers, four universalserial communication interfaces (UCSI) supporting enhanced universalasynchronous receiver/transmitter (UART), an Inter-Integrated Circuit(I²C) and Synchronous Peripheral Interface (SPI) and a primary bootstraploader with Joint Test Action Group (JTAG) interface to allow programdevelopment and memory programming.

The flash memory may be used to contain manufacturing data such ascalibration information, patient specific data, and other constantswhich need to be kept in a permanent location, as well as a secondaryboot loader and application code. In one embodiment, the secondary bootloader is required to allow transfer of code and data to the flashmemory after the IPG 1370 is welded closed (JTAG programming may nolonger be possible). The secondary boot loader may be stored in alocation which is reserved for its use and, as viewed by themicrocontroller, is actually the main application as it is activatedupon power on reset (POR) (the reset vector points to the boot loader).The secondary boot loader may initialize the system and wait for afinite period of time before either responding to manufacturing softwareloader commands or if no commands are received jumps to the main systemapplication. This architecture allows changes to be made in the flashmemory of the device once the JTAG interface is no longer accessible(such as field upgrades to IPG 1370 device firmware). Should changes benecessary to the secondary boot loader program, highly specializedprogram images may be written that when executed can write a new imageto the region occupied by the previous secondary boot loader.

The schematic diagrams for the IPG 1370 are shown in FIGS. 17 through21. Beginning with FIG. 17 is the lithium battery, the charge coilcircuit, battery monitor circuit, the battery disconnect circuit, thelithium ion battery charging circuit, the Vcc regulator circuit, the5V/10V/20V supply enable and voltage regulator circuits. A resettablefuse may protect the battery from over discharge and the battery monitorcircuit may protect the battery from under-voltage conditions. At 3.1V,IC2 monitor circuit may generate an open-collector low level whichdrives the analog switch IC1 to disconnect the battery from the systemVBatt signal. The signal S_Batt may be driven from an I/O port on themicrocontroller to enable battery disconnection under program control toallow the IPG 1370 to be placed into a low power shelf mode for longterm storage without battery depletion. Upon disconnection of thebattery, re-connection may be enabled upon application of a charge fieldto the charge coil. The charge field may be bridge rectified and zenerlimited and supplies power to voltage regulator IC5, which in turndrives battery charger IC6 to replenish power to the battery and tosupply system power. Battery power and charge power may be isolated fromeach other by diodes D1 and D2. Upon application of charge power andre-connection of the battery the microcontroller goes through its PORsequence and starts executing its primary and secondary boot loaders,described below.

FIGS. 18A and 18B depict an embodiment of the microcontroller and logmemory circuits, as well as the manufacturing JTAG communicationsconnections. The microcontroller may contain all system memory with theexception of event log memory which is interfaced to the microcontrollerusing an I²C interface. This non-volatile memory may be organized as aring buffer to keep only the latest events that occur during systemoperation. Optionally, log memory may be contained as well within theFlash memory space of the microcontroller.

FIG. 19 depicts an embodiment of the six channel current ASIC used forpulse generation and the series output capacitors used to prevent DCcurrent leakage. A manufacturing test load is shown, which may beremoved from the PCB after testing is completed. An analog multiplexeris shown which may allow voltage samples to be taken to measureelectrode/tissue impedances and compliance voltage levels. The sixchannel current ASIC is comprised of six identical current sourcesorganized with shift register interface to the microcontroller, datalatches for amplitude settings, and on-chip current mirror referencesand control circuitry. Each shift register may be driven individually ormay be daisy-chained for drive from a single data line. Clock lines,selects, address lines and enable lines all coordinate the transfer ofdata into the current source logic. The current sources are referencedto the 10V supply and supply biphasic current using the ground and 20Vsupplies for source and sink current generation. The current sources mayuse quasi-logarithmic methods with eight bit data plus sign bit tocontrol the level of current supplied. The logarithmic scale may beapproximated by eight linear segments with their own current step andoffset, resulting in very fine current steps at low amplitudes andprogressing to coarser steps as the current reaches its maximum levels.

FIG. 20 depicts an embodiment of the MICS telemetry circuitry and loopantenna located in the silicone header of the IPG 1370. The MICStelemetry circuit uses the 400 MHz band to transfer data to and from theIPG 1370 using secure data packets with RF identification, deviceidentification, command parsing and sixteen bit cyclic redundancy check(CRC16) codes to detect errors in the data transfer process. FIG. 21depicts the connectors that may allow the two PCB assemblies of the IPG1370 electronics to be attached together along with a test board thatallows the boards to be connected in a flat setting suitable fortesting.

Remote Control and Charger (RCC)

The Remote Control and Charger 2272 (RCC) is a handheld device which maybe used by the patient to operate and wirelessly charge their IPG 1370,and by the physician and clinical engineer to program the IPG 1370. Toserve these two roles, the RCC 2272 may operate in two modes. In theprimary mode, the RCC 2272 may respond to key presses on its membraneswitch panel, perform the functions requested, and display the resultson its front panel LEDs. In the secondary mode, the RCC 2272 may act inpass-through fashion, receiving commands from the aura Clinical Manager(aCM) software via a Universal Serial Bus (USB) connection to a personalcomputer (PC), and transferring those commands to the IPG 1370 throughits MICS telemetry interface. Responses and data from the IPG 1370 maybe received by the RCC 2272 and passed back to the aCM. In similarfashion, the RCC 2272 may be used in the manufacturing process whenconnection through the JTAG interface is not available. The front panelof the RCC 2272 with its keyboard and LED user interface is depicted inFIG. 22.

In one embodiment, the RCC 2272 is housed in a plastic enclosure,containing either a set of secondary nickel metal hydride (NiMH) AAbatteries or alkaline AA batteries, a printed circuit board (PCB)assembly, a membrane switch panel and LED displays. The batterycompartment may be accessible by the patient to replace the rechargeablebatteries should they wear out, or use alkaline AA batteries whentraveling. Located just above the battery compartment are metal contactsthat provide connection to the internal charging circuitry of the RCC2272. When the RCC 2272 is placed upon the docking station 5378, thesemetal contacts may align with spring loaded metal contacts in thedocking station 5378 which provide power to the RCC 2272 to recharge theRCC 2272 when it is not in use by the patient.

The RCC 2272 may have two connectors: one is a mini-USB connector usedto connect to the aCM PC, and also allows charging of the internalbattery. The second connector is a four pin circular connector whichconnects the RCC 2272 to the Charger Coil (CC). The CC may receive powerand control signals from the RCC 2272 and allows a secondary inductivelink channel to transfer and receive information with the IPG 1370should the MICS telemetry link be non-functional. The second four pinconnector may also be used during sleep laboratory tests to provide anindicator to the clinician which stimulation group is active. A specialcable may be provided that interfaces to the various brands of PSGequipment.

The RCC elements are shown in the block diagram FIG. 23 and may consistof a 16 bit microcontroller, a MICS telemetry transceiver, inductivepower interface circuitry, battery charging circuitry, power suppliesand analog signal acquisition support circuitry. The microcontroller mayhave a large number of resources, including a 16 bit reduced instructionset core (RISC), 92 KBytes of Flash memory, 8 KBytes of RAM, a threechannel DMA, a 12 bit A/D and D/A, 16 bit timers with 10 capture andcompare registers, four UCSI ports supporting enhanced UART, an I²C andSPI protocols and a primary bootstrap loader with JTAG interface toallow program development and memory programming.

The flash memory may be used to contain manufacturing data such ascalibration information, patient specific data, and other constantswhich need to be kept in a permanent location, as well as theapplication code. Unlike the IPG 1370, the RCC 2272 can always beupgraded to new firmware through the USB interface or the JTAGinterface. Exemplary schematic diagrams of the RCC 2272 are shown inFIGS. 24 through 28. The flash memory of the RCC 2272 may also be usedto log events in a similar manner to the IPG 1370.

FIG. 24 depicts the connection to the Docking Station 5378 and to theUSB connection. The docking station 5378 may transfer 5V from a USB wallmount charger to metal contacts on the underside of the RCC 2272chassis. This 5V signal may be fused and zener protected before beingbrought to internal circuit elements of the RCC 2272. The USB connectormay be additionally capable of supplying 5V power, as well as providingthe communication link to the aCM through circuit IC1, a USBtransceiver. The Docking Station may have its own internal power supplyand the USB connector may be replaced by a power cord connection tohousehold power.

FIG. 25 depicts the connection to an internal three AA cell batterypack, typically comprised of NiMH cells, or alkaline cells. The NiMHcells can be recharged, the alkaline cells can be replaced. The batterymay be protected from over discharge by a resettable fuse. In oneembodiment, power from the previous diagram is used to power the NIMHcharger circuit, IC2. From either the power from the previous circuit orthe battery a Vcc 3.3V regulator, IC3, may provide system power for themicrocontroller and other logic. In one embodiment, power may also besupplied to IC4 which generate the 6V or 8V supply for operating thecharging coil, which supplies power to the IPG 1370 for charging itsinternal lithium ion battery.

FIGS. 26A and 26B depict an embodiment of the microcontroller and JTAGprogramming interface. Unlike the IPG 1370 which may lose its JTAGinterface after programming and test in manufacturing, the RCC 2272retains this connector in the finished assembly. FIG. 27 depicts theMICS telemetry transceiver circuit and the connection to an SMA type RFantenna which is housed inside the plastic enclosure of the RCC 2272.FIG. 28 depicts an exemplary user interface—a membrane switch panel, andthe multi-color LEDS for the front panel. The LEDs may be driven by anI²C interface port expander, IC7. In one embodiment, light from the LEDsis transferred from their position on the PCB to windows in the membraneswitch panel through clear light pipes. A piezo buzzer may be drivenfrom this same interface for provision of audible tones for the user.Exemplary membrane switch panel artwork is depicted in FIG. 22.Alternatively the RCC may provide an LCD display instead of or inaddition to the LEDs.

Charger Coil (CC)

The Charger Coil 5374 a (CC) may be a small device attached by aflexible cable to the RCC 2272 when it is necessary to charge the IPG1370. An exemplary block diagram for the

CC is shown in FIG. 29. In one embodiment, the CC assembly is comprisedof a PCB housing the electronics necessary for its operation, the optionof an embedded coil structure or a mounted inductive coil, and a magnetwhich aids in the alignment and retention of the CC to the IPG 1370. TheIPG 1370 may contain a similar magnet in its inductive loop coil locatedin the header of the IPG 1370. Much like a cochlear implant, this simplealignment and fixation method may assure that the best possible energytransfer between the CC and the IPG 1370 occurs with as little impactupon the patient as possible.

Docking Station (DS)

The Docking Station 5378 (DS) may provide a convenient place on thepatient's night stand to place and charge the RCC 2272 when it is not inuse. Having convenient alignment and holding features, the patient canplace the RCC 2272 into the DS 5378 in a single simple motion. The RCC2272 may be easily removed as well for use when the patient wishes tooperate the IPG 1370. In one embodiment, the DS 5378 has contacts on itstop surface which mate with matching metal contacts in the RCC 2272. TheDS 5378 may have a mini-USB connector for attachment to a wall-mountedUSB charger. The charger can be unplugged from the DS 5378 and travelwith the RCC 2272 to allow the RCC 2272 to be charged when the patientis traveling. The DS 5378 may have its own integrated power supply thatuses a standard wall plug to acquire power.

aura Clinical Manager (aCM)

The aura Clinical Manager (aCM) is a software application running on apersonal computer. In one embodiment, the aCM is used by the clinicalengineer or clinician to program an IPG 1370 and an RCC 2272 for aparticular patient, and to fit and optimize a stimulation therapy forthe patient. The aCM can run on a standard PC.

Memory, or alternatively one or more storage devices (e.g., one or morenonvolatile storage devices) within memory, includes a computer readablestorage medium. In some embodiments, memory or the computer readablestorage medium of memory stores programs, modules and data structures,or a subset thereof for a processor to control the RCC 2272, IPG 1370and other system components described herein.

The aCM functionality may be divided along its use model applications,selected by a series of tab selections along the left edge of thescreen. A local database on the computer may be maintained andsynchronized automatically whenever an internet connection is providedto the computer. Database synchronization to the host database mayensure backup of all patient data and tracking of patient use of theimplanted systems.

Patient Manager Screen

In one embodiment, the first screen is the Patient Manager screen, andis shown in FIG. 30. It is with this screen that a patient is firstentered in the patient database and data collected pertaining to thepatient's particular case of OSA. Existing patients may be located inthe database by selecting the “Find Patient” and the system is able tofind patient records that resemble the entry made by the user. Once arecord is displayed, it can be selected. Reports may be generated for apatient on this screen as well and may be formatted for HTML for viewingas a file in a browser, such as Internet Explorer or Safari.

OSA system components may be issued to the patient and their issue dateand serial numbers, as well as other pertinent information may beentered in the patient database as well. When elements of the system arereplaced due to wear-out, loss, or failure, etc., the new elements maybe entered into the database in a similar manner. Once all of theinformation for the patient is entered, the user may select any of theother screens.

Implant/Surgery Screen

The Implant/Surgery Screen may be the primary screen used by theclinical engineer or clinician to test the OSA system during thesurgical implantation of the IPG 1370 and electrode. It is used in theoperating room (OR) to test the system elements, to verify electrodeimpedances are in an acceptable range, and that the HGN 322 response tostimulation and threshold levels are acceptable.

Titration Screen

The Titration Screen, an exemplary embodiment being depicted in FIG. 31may be the primary screen used by the clinical engineer or clinician tofit the OSA system to the patient. Following surgery, approximately aweek or more later, the Titration Screen of the aCM may be used for themain programming session for the patient. It is at this session whereall of the stimulation parameters may be determined in preparation for asleep study to verify the operation of the system in providing therapyfor the OSA condition.

In one embodiment, the Titration Screen is divided into six sections.The largest section may be dedicated to Amplitude control whereThreshold, Target and Maximum current amplitudes are determined for eachof the six contacts of the system. Convenient Quick Set buttons may beprovided to allow the amount of current at which amplitude changes witheach increment or decrement of the up and down arrows, marking ofThreshold, Target, and Max levels, and the setting of all enabledcontacts to their Threshold or Target levels. In one embodiment, just tothe right of this area are six slider controls with enable boxes toallow each contact to be tested individually or in concert with othercontacts. When the Threshold is observed, selecting the Set Thresholdbutton will transfer the value of the current for that contact to theThreshold box below the slider and a colored bar marker will be placedon the slider window at the current level. When the Target level isobserved, selecting the Set Target button will transfer the value of thecurrent for that contact to the Target box below the slider and anothercolored bar marker will be placed on the slider window at the currentlevel. When the Maximum level is observed, selecting the Set Max buttonwill transfer the value of the current for that contact to the Maximumbox below the slider and yet another colored bar marker will be placedon the slider window at the current level. Threshold may be tested at 1Hz while Target and Maximum may be selected at 15 Hz (or any otherdesired frequency that is greater than 1 Hz). Below each slider bar foreach contact is an effect indicator, selected by a pull-down box, wherethe effect of the stimulation applied to the electrode is indicated(protrusor, retrusor, no effect, etc.).

The section directly below the contact slider controls may be theContact Impedances section, and provides a quick way to request andreceive contact impedance with respect to the case indifferent electrodeof the IPG 1370. To the right, at the top, is the Status window. In theStatus window the aCM to RCC USB communication status may be shown, theRCC 2272 to IPG 1370 MICS telemetry communication status may be shown,and the RCC 2272 and IPG 1370 Battery levels may be shown. In oneembodiment, directly below this is the Frequency window in which thestimulation frequency may be set by increment or decrement, or quicklyset to 1 or 15 Hz (same as pulses per second, or pps), with theresultant frequency shown below the up down buttons. In one embodiment,directly below the Frequency window is the Saving and Restoring window.This window may be used to save and recall program settings and patientdata in a time and date stamped entry into the local patient databasefile. Multiple data records can be stored for a patient on the same day,and provision is made to annotate the records with a short field forquickly locating a record, along with a more detailed record that allowsclinician descriptions of the actions taken to be captured. In oneembodiment, the last window is the Stimulation Control window, and isused to start and stop stimulation.

PSG Screen

The PSG screen may be used during sleep laboratory studies to optimallyallow easy manipulation of stimulation parameters by 5% variances and toallow monitoring of the IPG 1370 status during the test. Because the IPG1370 operates independently, it is not easily discerned whichstimulation group is active at a particular time. It is beneficial toidentify which stimulation group is active to correlate this informationwith the data visible during the PSG test to verify that stimulationlevels for that group are adequate or in need of adjustment. Normallythe IPG 1370 only responds to commands received from a validated sender.In the PSG setting, the IPG 1370 may be enabled to transmit messagesindicating when groups change, when channels ramp up or down, whengroups delay and when they are in plateau phases. This information issent to the RCC 2272 which can, using its four pin connector, generatesignals that can be monitored by the PSG system to allow indication ofIPG 1370 activity to be recorded with all of the other PSG measurements.In addition, the aCM can use its USB connection to the RCC 2272 toperiodically inquire what the status of the IPG 1370 is and display thatinformation on a location within the PSG screen.

Manual Parameter Control Screen

The Manual Parameter Control Screen, an exemplary embodiment beingdepicted in FIG. 32 may be used to set parameters that are typically notchanged from their default values, but which might be changed undercertain conditions. In one embodiment, the screen is divided into twomain sections—one in which stimulation parameters and logs may beviewed, and another section with status and data transfer operations areconducted. The top left sections may be used for setting and viewingGlobal IPG Parameters, such as Startup Delay (or Sleep Session Delay),Pause Delay, etc., while the section just to the right is the GroupParameters section. Groups can consist of as few as one electrodecontact, or as many as six. Groups default to one contact each, with thefirst group containing contact one., the second group containing contacttwo, and so on. In situations where multiple contacts belong to a groupthe percentages of contribution for each group are entered into theirrespective locations. This controls the distribution of current and thussets the field of neural activation between two or more contacts of thecuff electrode 764. Below the Global IPG Parameters window may be theElectrode window, and if a contact is enabled, its current settings maybe displayed as will be the effect it causes. Manual entries into thefields of this section are allowed, but changes to amplitude will becorrected to the nearest actual amplitude possible. This may be requiredbecause the output of the current sources in the IPG 1370 islogarithmic, not linear, so manual selection of amplitude is not as easyas it would seem. The increment and decrement function of the Titrationscreen automatically takes this non-linearity of the current sourcesinto effect and uses the calibration data of the IPG 1370 to displayactual currents.

The main section to the right may contain a Status Window again, and twosections that control communication between the RCC 2272 and IPG 1370and File Operations. In the Communication section, stimulationparameters may be read from or sent to the IPG 1370. In the FileOperations section, stimulation parameters may be read from or writtento records in the database. IPG 1370 event logs may be retrieved fromthe IPG 1370 and saved to files as well. In one embodiment, the bottomportion of the Manual Parameter Control screen allows the viewing of thevarious logs that are collected by the IPG 1370, including electrodeimpedances, battery charging operations, battery use profiles, and IPGevents, both expected and unexpected (but anticipated) events.

RCC Functions Screen

The RCC Functions Screen, an exemplary embodiment being depicted in FIG.33 may allow the aCM to fully simulate the operation of the RCC 2272while the RCC 2272 is connected to the aCM and is in pass-through mode.Indicators for the LEDs and regions on the screen that can be clickedlike the buttons of the RCC 2272 switches allow full operation of thesystem as if the aCM were not connected. This may be useful when the aCMuser is located at a distance from the RCC 2272 (such as might occur inthe OR, sleep laboratory, or other remote location).

RCC USB Comm Screen

The RCC USB Comm Screen, an exemplary embodiment being depicted in FIG.34 may be a special screen that is typically only enabled for use by anengineer. The RCC USB

Comm Screen may allow complete observation of communications between aCMand RCC 2272 and between the RCC 2272 and an IPG 1370. In oneembodiment, manual formulation of telemetry commands is supported, aswell as computation of CRC codes to be included in command packets. Portoperations on the aCM are also visible and controllable in this screen.This may be particularly useful when certain PC platforms and versionsof Windows are used with USB devices and connect and disconnect of USBcables causes re-assignment of ports to occur, sometimes without obviousrhyme or reason to the user.

Operation of System

In one embodiment, operation of the system includes five phases ofoperation: Manufacturing, Implantation, Titration, PSG, Follow-up, andPatient use phases. During the Manufacturing phase, the IPG 1370 and RCC2272 may be programmed, tested, calibrated, and stocked for shipment andimplantation. The JTAG interface of the PCB assemblies of the IPG 1370(before singulation and encapsulation into its hermetic enclosure) andRCC 2272 may allow full programming and test to occur. Post singulationand encapsulation of the IPG PCB assemblies may require use of thesecondary boot loader described previously to change program contents ofthe IPG 1370. In one embodiment, following programming and testing of anIPG 1370, it may be placed into a low power consumption mode in whichthe battery is disconnected from the circuit and only very low currentconsumption occurs due to the single active component remainingconnected to the IPG battery, a battery monitoring circuit. This mayallow an IPG 1370 to be fully charged, then disconnected from itsbattery and stored for a long period of time with little loss of batteryenergy. In the programming environment a computer with a JTAG interfacemay be connected to the various assemblies and code may be programmedinto the devices. In the sealed IPG 1370, the programming system mayutilize a stock RCC 2272 to transfer commands over the MICS telemetryband to the IPG 1370.

The Implantation phase, an example being depicted in FIG. 35, occurswhen the patient is surgically implanted with the electrode and IPG1370. In this environment, the IPG 1370 and electrode may be containedin sterile packaging ready for use within the sterile field of theoperating room. Prior to surgery, an RCC 2272 may be placed on theoperating table next to the patient, and a long USB mini-B cable may beconnected to the RCC 2272 and crosses the border of the sterile fieldand may be passed to the clinical engineer and aCM. During theimplantation the IPG 1370 and electrode may be briefly tested forimpedance and threshold stimulation levels for all of the six contactsof the cuff electrode 764.

The Titration phase, an example being depicted in FIG. 36 may be themain programming phase for the system. In this phase, all contacts maybe tested to determine their threshold, target and maximum stimulationlevels, what the actions of each of the electrode contacts elicits,testing of contact pairs or tripoles, etc., if warranted, and assignmentof groups that may be used during the Patient Use phase. The Follow-upphase may be essentially just like the Titration phase, except thatchanges may be made to pre-existing stimulation parameters so thatimprovements in stimulation effect may be obtained or corrections due tocontact or wire failures or other causes can be mitigated. The PatientUse phase, an example being depicted in FIG. 37 may be the main use ofthe system and encompasses the stimulation therapy and maintenance ofthe OSA system. The detailed operations of the OSA system are describedin further detail below.

On/Off Button Pressed

The On/Off button on the RCC 2272 may be used to start or stop a sleeptherapy session. The procedure associated with the On/Off key operationis represented in FIG. 38. In one embodiment, the patient removes theRCC 2272 from the docking station 5378 and presses the On/Off key. TheRCC 2272, which may have been in a low power consumption mode, awakensand begins to search for its assigned IPG 1370. The RCC 2272 may sendtelemetry requests through its MICS telemetry channel for a fixed periodof time. If at the end of this time window it has not found its IPG1370, it may generate beeps, indicate a failure to link to its IPG 1370and end the sleep therapy session.

If the RCC 2272 is able to link to the IPG 1370, it may then send arequest for the IPG 1370 to send its status information, including stateof charge for the IPG battery, electrode impedance information, as wellas error flags and other information that is relevant prior to startinga sleep therapy session. The RCC 2272 may set LEDs indicating the statusof the IPG 1370. If there is sufficient charge in the battery to start asleep session, and if all of the electrodes programmed to operate arewithin operational boundaries then the IPG 1370 may be instructed tostart a sleep therapy session. The IPG 1370 may send the RCC 2272 a datapacket with the duration of the sleep session, which the RCC 2272 mayuse to control the indicator LED on its front panel showing the statusof the IPG 1370. The RCC 2272 may then go to sleep in a low power modeuntil the next time that the patient presses a key. The IPG 1370 may goabout the process of sleep therapy, described below.

Charge Button Pressed

The Charge Key may initiate the process of charging the IPG 1370, anexample being depicted in FIG. 39. In this process, the patient mayconnect a charger coil (CC) to the RCC 2272 and places the CC over theIPG 1370 to transfer energy from the RCC 2272 to the IPG 1370.

The RCC 2272 may be able to detect when the CC is attached because of aloop-back connection within the connector or by monitoring currentconsumption. In one embodiment, the CC is held in place over the IPG1370 because both devices could contain magnets which could help to holdand align the CC optimally over the IPG 1370. The RCC 2272 may be ableto determine how well the coil is aligned over the IPG 1370 bymonitoring the current consumption in the CC. By this same method ofmonitoring current and by changing the current in the CC a secondarytelemetry channel may be available in case of problems with the primaryMICS telemetry channel.

An exemplary sequence of events in the Charge process may be as follows.The patient presses the Charge button and the RCC 2272 may come out ofits low power mode. If the charge process is already in place, theintent of the patient may be deduced to be to end the charge process.The RCC 2272 may stop the charge process and disable the CC andestablish a MICS communication link with the IPG 1370. It then may thensend an end of charge command to the IPG 1370, turn off the Charge LED,and request the IPG 1370 status. It may then display the IPG batterystatus, and assess the impedance data. If the impedances are acceptable(within an acceptable range for current controlled pulses to begenerated), the charge process may end. If the impedances are not withinan acceptable range, then the On/Off LED may be set to red, the RCC 2272may generate beeps and the charge process may end. If the charge processwas not already set, the RCC 2272 may set the Charge LED to green andstart the IPG Charge process, described below.

Test Button Pressed

The Test button may initiate a process to demonstrate to the patient abrief stimulation session that is representative of the stimulation thatwill be applied during the sleep session. Since the stimulation duringthe sleep session may not actually begin to deliver stimulation pulseswhile the patient is awake, it may sometimes be desirable for thepatient to verify that the stimulation system actually will work asexpected, or to verify that the stimulation parameters will becomfortable during the sleep therapy. The test process may be identicalto a sleep therapy session except for the duration of the stimulationperiods, the on and off times, and the ramp times for all of the groups.In one embodiment, stimulation starts immediately upon initiation of thetest process and ends after all of the groups have gone through theirramp up, plateau, and ramp down phases, or when the test button ispressed again to stop the test process immediately. The sequence ofevents in the Test process is shown in FIG. 40. After the Test key ispressed, the RCC 2272 may come out of low power mode and seeks the IPG1370. If the RCC 2272 cannot find the IPG 1370, the RCC 2272 maygenerate beeps, set its LEDs and the test session quits. If the IPG 1370is found, the RCC 2272 may request the IPG 1370 status. The RCC 2272 maythen set the IPG 1370 battery status LEDs appropriately. If the Batteryis sufficiently charged, the RCC 2272 may then continue, otherwise thetest process could quit. If the impedance is within acceptable limitsfor the active groups then the test command may be sent to the IPG 1370,if not, the RCC 2272 may generate beeps, set the Test LED to red and thetest session may end.

Pause Button Pressed

The Pause button may stop a stimulation session for a brief period toallow the patient to wake up and go to the bathroom, etc. An exemplarypause process is outlined in FIG. 41. The key may only valid during asleep therapy session and may be ignored if the IPG 1370 is not in thismode. An exemplary RCC 2272 pause process may be as follows: the patientpresses the Pause key. If the IPG 1370 is not in a sleep session, theRCC 2272 beeps, turns off LEDs and returns to low power mode. If the IPG1370 is in a sleep session the RCC 2272 attempts to link to the IPG 1370and requests the status of the IPG 1370. If the IPG 1370 is not alreadypaused, the RCC 2272 sends a pause command to the IPG 1370, sets thePause LED green, and returns to low power mode. If the IPG 1370 wasalready in pause mode, the RCC 2272 may look at the IPG battery. If thebattery is low, the RCC 2272 may end the sleep session and set the IPGLED to red and return to low power mode. If the battery is full the RCC2272 may set the IPG LED to green, otherwise the RCC 2272 may set thebattery LED to amber. The RCC 2272 may then check the impedance. If theimpedance is not OK the RCC 2272 may set the On/Off LED to red, generatebeeps, and return to low power mode. If the impedance is OK, then theRCC 2272 may turn the Pause LED off. The RCC 2272 may then check to seeif the sleep duration is over. If so, it may set the On/Off LED to offand end the sleep session. If the sleep session is not over the RCC 2272may send a command to the IPG 1370 to finish the pause and the RCC 2272may go back to low power mode.

IPG Pause Process

The IPG 1370 Pause Process may occur upon command from the RCC 2272, andan example is depicted in FIG. 42. An exemplary IPG Pause process mayproceed as follows: If the IPG 1370 is not in a sleep session the IPG1370 may return and go back into low power mode. If the IPG 1370 is notin the pause mode the IPG 1370 may enter the pause mode, suspendstimulation and return to its low power mode. If the IPG 1370 is in thepause mode the IPG 1370 may start to return to stimulation mode, ifseveral conditions are met. First the IPG 1370 may check to see if thebattery is low, and if is the battery is low, the IPG 1370 may sendstatus information to the RCC 2272 and end the sleep session. If thebattery is not low, the IPG 1370 may check impedances. If the impedancesare not within an acceptable range, then the IPG 1370 may send statusinformation to the RCC 2272 and end the sleep session. If the impedancesare within an acceptable range, then the IPG 1370 may load the UnPausedelay (similar to the sleep session delay, but typically less timebecause most patients will fall back to sleep faster than at thebeginning of the sleep session), wait for the delay to be complete, andthen the IPG 1370 may start setting up the first group for stimulation.This may involve setting up the startup frequency delay, the startupfrequency duration, the group one ramp up duration, the group one ontime, the next group delay time, the amplitude threshold, setting thefrequency ramp to active, setting the ramp to active, setting theplateau phase to inactive, setting the ramp down to inactive, andenabling stimulation. The IPG 1370 then may then return to the low powersleep state.

IPG Charge Process

The IPG Charge Process may be initiated by the RCC 2272, as describedabove, and an example is depicted in FIG. 43. In one embodiment, the IPG1370 and the CC are coupled, the RCC 2272 is close enough for MICStelemetry, the RCC 2272 is completely charged and able to transfer powerto the IPG 1370, and all other relevant systems are functional. The RCC2272 and IPG 1370 may share in the responsibility of checking that theCC is attached to the RCC 2272 and that the CC is aligned properly overthe IPG 1370. With everything in place, the RCC 2272 may then enable theCC. The RCC 2272 may then choose a charge duration based upon the stateof charge of the IPG battery. If the battery voltage is less than acertain level the RCC 2272 may set the charge duration to 30 minutes. Ifthe battery voltage is less than a slightly higher level the RCC 2272may set the charge duration to 20 minutes. Otherwise the RCC 2272 mayset the charge duration to 10 minutes. The RCC 2272 may then wait forthe charge duration to be over, after which the RCC 2272 may disable theCC and request the status from the IPG 1370 and set its LEDsaccordingly. If the battery is full, the RCC 2272 may generate beeps,set Charge LED green for 10 seconds and end the charge process. If not,the RCC 2272 may check the temperature of the IPG 1370. The temperatureof the IPG 1370 would be checked to see if a potentially dangerous ordetrimental condition exists because of the charging process and theeffect that can have on the chemistry of the rechargeable battery. Ifthe temperature of the IPG 1370 is acceptable the RCC 2272 may then goback to choose the charge duration and continue the charge process. Ifthe temperature is not acceptable, the RCC 2272 may generate beeps, setthe Charge LED to red for 10 seconds, and end the charge process. At theend of a fixed duration the RCC 2272 may terminate the charge sessionregardless of the state of charge of the IPG battery.

Sleep Session Process

An exemplary sleep Session process is depicted in FIG. 44. The IPG 1370may load the sleep duration counter, load the startup delay and thenwait for the startup delay to be completed. The IPG 1370 may thenprepare the first stimulation group. The startup frequency may then beloaded, the startup frequency duration may be loaded, the first groupramp duration may be loaded, the group on time may be loaded, the nextgroup delay may be loaded, the amplitude threshold(s) may be loaded, thefrequency ramp may be set to active, the ramp up may set to active, theplateau phase may be set to inactive, the ramp down may be set toinactive, and the IPG 1370 may return to the low power sleep state.

Frequency Tick Process

The Frequency Tick Process may be the main event coordinating thedelivery of stimulation pulses. Since the frequency tick interruptprocess represents the frequency that pulses occur during stimulation,the timer interrupt associated with this event may be therefore theevent which triggers the delivery of a set of pulses for all of theactive contacts and the advancement from one phase to another for agroup, or the transition between groups. Typically, it is expected thatwhen a group is at its plateau or target level it will be the only groupactive, but during the ramp up and ramp down times there may be two ormore groups active, depending upon the intent of the programmingprocess.

The Frequency Tick Process is depicted in FIG. 45. The IPG 1370 firstchecks to see if the frequency ramp is active. If yes, the IPG 1370 maymake any necessary changes in the timer value used to generate thefrequency tick interrupt, thereby adjusting the frequency and then maydecrement the frequency ramp duration. The IPG 1370 then checks to seeif the frequency ramp duration is zero. If the frequency ramp durationis zero, the IPG 1370 may set the frequency ramp to inactive. The IPG1370 may then begin to service the current active group. The IPG 1370first checks to see if ramp up is active. If ramp up is active, the IPG1370 may make any necessary adjustments to the group amplitude level.The IPG 1370 then may decrement the ramp duration and then checks to seeif the ramp up duration is zero. If the ramp up duration is zero, theIPG 1370 may de-activate the ramp up phase and may activate the plateauphase. Next the IPG 1370 checks to see if the plateau phase is active.If the plateau phase is active, the IPG 1370 may set the amplitude atthe target level, decrement the plateau duration, and check to see ifthe plateau duration is over. If the plateau duration is over, the IPG1370 may deactivate the plateau phase and activate the ramp down phase.Next the IPG 1370 may check to see if the ramp down is active. If theramp down is active the IPG 1370 may adjust the amplitude as needed,decrement the ramp down duration and check to see if the duration iszero. If the ramp down duration is zero, the IPG 1370 may inactivate theramp down phase and deactivate the group.

Next the IPG 1370 may check to see if the battery is chargedsufficiently. If the battery is not sufficiently charged, the IPG 1370may end the sleep session and return to low power mode. Next the IPG1370 may check the impedances. If the impedances are not withinacceptable limits the IPG 1370 may end the sleep session and return tolow power mode. Next the IPG 1370 may generate the pulses for the activegroup. Next the IPG 1370 may look to see if another group is active, andif so begins to service that group as indicated above. If not, the IPG1370 may return to low power mode.

Next Group Tick Process

The Next Group Tick Process, depicted in FIG. 46 is responsible foractivating the next group in the stimulation process. When the timerinterrupt associated with the Next Group Delay Tick occurs, the IPG 1370may decrement the next group delay counter, and check to see if thedelay counter is zero. If the delay counter is zero, the IPG 1370 mayactivate the next group, load the ramp up duration, load the group ontime, load the next group delay, and load the amplitude threshold andthen return to low power mode. If the counter is not zero the IPG 1370may simply return to the low power mode.

Sleep Duration Tick Process

The Sleep Duration Tick Process, depicted in FIG. 47 is responsible forcontrolling the duration of the sleep therapy. The end of therapy may ormay not coincide with the ramp down of the currently active group(s). Inthe process, upon the timer interrupt assigned to the sleep duration,the duration may be decremented, and if zero, the sleep session may beended and the IPG 1370 may return to a low power mode. If the durationis not zero the IPG 1370 may simply return to the low power mode. Itshould be recalled that the sleep duration may be sent to the RCC 2272by the IPG 1370 at the beginning of the sleep treatment session. The RCC2272 may independently count down its own copy of this value, and whenthis count reaches zero the RCC 2272 may set the LEDs of the RCC 2272accordingly. No communication between the IPG 1370 and RCC 2272 may needto occur at the end of the therapy session.

Group On Time Tick Process

The Group On Time Tick Process is depicted in FIG. 48, and occurs whenthe timer interrupt associated with the group on time counter occurs.When this event occurs, the group on time may be decremented, and if thecounter value reaches zero, the group may be disabled. This is aredundant process to the frequency tick in that both processes are ableto control the duration of a group, but may be used in some instanceswhen specific on times are desired that are different than the sum ofthe ramp up, plateau, and ramp down phases.

Impedance Measurement Process

The Impedance Measurement Process is depicted in FIG. 49. Impedances maybe regularly measured for all active contacts by measuring the voltageacross the contact with respect to a reference, and knowing the currentat which the stimulus pulse was generated, the impedance of the contactmay be calculated. When impedances are detected on contacts that areprogrammed to participate in stimulation groups that fall outside ofacceptable bounds, then stimulation from that point forward may besuspended. Upon noticing that stimulation cannot be started, the patientmay be instructed to seek the advice of their physician, who couldre-program their IPG 1370 to use other contacts, if possible, or toschedule revision surgery to correct the problem. An error flagassociated with the measurement process may be updated and utilized fordetection of out of bounds impedances for the stimulation process.

The impedance measurement process may begin with the initialization ofseveral items. First, the total number of channels (contacts) may beloaded, the sample count loaded, the sample accumulator cleared, thesample rate set, and the impedance error flag may be cleared. Thesampling process may then begin. The impedance for the first contact maybe read and added to the accumulator. This may repeat until the lastsample is read. Next an average value may be computed and stored in theimpedance array for the contacts. If the channel/contact was active, theimpedance may be checked for validity. If the impedance is outside therequired bounds the impedance error flag may be logically OR'ed with thebit value for the channel. If that was not the last channel, the samplecount may be re-loaded, the accumulator cleared, and the process beginsfor the next channel/contact. If the last contact/channel tested was thelast channel/contact, the impedance data and error flag may be stored,the impedance data reported back to the RCC 2272, and the IPG 1370 maygo into the low power mode.

Boot Loader Process

The Boot Loader Process (meaning the Secondary Boot Loader, and do notdiscuss the primary boot loader of the microcontroller) is depicted inFIG. 50, and may be the default program of the IPG 1370 processor—i.e.,the Boot Loader Process is the program associated with the reset vectorof the microcontroller of the IPG 1370. This boot loader may be requiredbecause the mask read-only-memory (ROM) boot loader of themicrocontroller may only support a JTAG or similar interface to debug orprogram the flash memory of the microcontroller, and when the PCBassemblies are welded into the IPG 1370 case there may be no alternativemethod to re-program the IPG 1370 other than this secondary Boot Loaderprocess.

The IPG 1370 can be placed into a power off state by being commanded todisconnect the battery from the IPG 1370 main circuitry. Once thiscommand is executed, the only portion of the IPG 1370 circuitry beingpowered may be the battery monitor. This mode may be used to store theIPG 1370 in shelf mode, while it is awaiting shipment to a customer. TheIPG 1370 may be taken out of the shelf mode by application of chargerinductive power. This may supply power to the processor, which with itsPower On Reset (POR) sequence, may vector to the Boot Loader. The BootLoader may initialize the microcontroller and IPG 1370 resources, log anevent that the Boot Loader has done so, open the MICS telemetry channel,load a Boot Message timeout counter, and wait for an incoming messagefrom the RCC 2272. If no message is received before the timeout counterreaches zero, then the boot loader may check to see if there is a validapplication image. If not, the Boot Loader may disconnect the batteryand return to shelf mode. If a valid application image is available,then the Boot Loader may call the application. The use of a callinstruction may allow a jump to any space in program memory without theexpectation that a return from the application will occur.

Main Application Process

The Main Application is depicted in FIG. 51. The main application may becalled by the Boot Loader, and may be responsible for initialization ofsystem resources, servicing RCC 2272 telemetry commands, and monitoringsystem operation. The Main Application may proceed from power up byinitializing the system, log a “begin main application” event, enableMICS wakeup interrupts and enter a low power mode. Upon receiving MICSwakeup interrupts the IPG 1370 may service the RCC 2272 command, load aMICS timeout window value, and await another command. When the timeoutreaches zero, the main application may re-enable the MICS wakeupinterrupt and may then go back into low power mode. The application mayspend as much time as possible in low power mode to conserve batteryenergy for the convenience of the patient. All processes may essentiallyoccur as needed by interrupt mechanisms. Interrupts, and thus processes,may be prioritized and masked or enabled as needed, to control theorderly operation of the IPG 1370. This may be extremely important toallow concurrent operations such as telemetry during stimulation, toallow changes in stimulation to be commanded by the RCC 2272 and theaCM. Without this interrupt concurrent system design there could beunacceptable latencies in certain events, which could manifestthemselves as apparent lack of operational capability or delays to thepatient or clinician.

System Programming

System programming and stimulation of the exemplary embodiments do nothave to take into account the timing of respiration. When electricalstimulation is applied to a nerve bundle there are essentially twofactors that determine which fibers within the bundle will be excited.The first is distance of the fiber to the contact—the closer a fiber isto the contact, the higher the current gradient and the more likely thatthe fiber will be excited. The second is the diameter of the fiber,which determines the voltage changes across the membrane and hence thelikelihood of reaching the threshold of generating an actionpotential—the larger the diameter, the more likely that the fiber willbe excited. At a particular current amplitude of sufficient duration,all of the fibers within a certain distance or diameter of thestimulation will be excited. As current amplitude increases, more fiberswill be excited. Since each fiber is associated with a muscle fiber orfibers (jointly referred to as a motor unit), as more nerve fibers areexcited, more muscle fibers are caused to contract, causing a gradationin force production or position as the stimulation current or phaseduration is increased. The point at which this force is first generatedis referred to as the motor threshold, and the point at which all of thefibers are all recruited is the maximum stimulation level. The comfortof this activity to the patient is often exceeded before this maximumlevel is attained, and it is important to determine the threshold leveland the level at which the useful level of force or position is obtainedat a level that is not uncomfortable for the patient. The point at whichthe optimal or best possible force or position is obtained is the targetlevel.

In certain exemplary embodiments, system programming entails operativelyconnecting at least one electrode with a motor efferent located within anerve (for example, the Hypoglossal nerve). This connection need not bea physical connection. The connection can be any connection known tothose skilled in the art where the connection is sufficient to deliver astimulus to the targeted motor efferent of the targeted nerve. Once theelectrode is operatively connected with the targeted nerve, two or moreelectrode contacts are activated to determine their applicable stimulusthresholds (i.e., the threshold at which a desired response isachieved). The level of stimulation comfortable to the patient can alsobe measured. The contacts may also be assigned into functional groupsthat provide tongue motions that are beneficial in maintaining airwaypatency.

In certain exemplary embodiments, stimulation may be provided to thenerve using at least two functional groups. A functional group isdefined as one or more electrode contacts (for example contacts 764 a,764 b, 764 c and 764 d shown in FIGS. 7 and 8) that deliver a stimulusthat results in a tongue movement that maintains an open airway. Eachfunctional group may have a single contact, or may have multiplecontacts. For example, a functional group with two contacts could beused to excite a population of nerve fibers that lie between twoadjacent contacts. A non-limiting example of how stimulation from thefunctional group can be delivered is field or current steering,described in International Patent PCT/US2008/011599, incorporated byreference in its entirety. In another exemplary embodiment, two or moreadjacent contacts may be used to focus the stimulation field to limitthe area of excited neurons to a smaller area than what might beachieved with a single contact using a pulse generator case as a returncontact. In another exemplary embodiment, two or more non-adjacentcontacts may be used together to generate a useful response that isbetter than the response by the single contacts alone could produce. Thetable below shows various exemplary combinations of functional groupsfor an embodiment having six contacts numbered 1-6. A single contact canbe a member of more than one functional group. For example, contact twocould be in two different groups—one group made up of contact 1 and 2,and another group made up of contact 2 and 3. Exemplary contact groupsare shown below.

a. Single Contact Groups: 1,2,3,4,5,6

b. Double Contact Groups: 1&2,2&3,3&4,4&5,5&6,6&1

c. Triple Contact Groups: 1&2&3,2&3&4,3&4&5,4&5&6,5&6&1,6&1&2

d. Non-Adjacent Contact Groups: 1&3, 2&4, 3&5, 4&6, 5&1, 1&3&5, 2&4&6,3&5&1, 4&6&1, 1&2&4, etc.

FIG. 9 illustrates an exemplary stimulation strategy. FIG. 52 provides amore detailed view as the stimulation transitions from one active groupto the next. As shown in FIG. 9, functional groups may be used toestablish load sharing, amplitude ramping, and delayed start ofstimulation to optimize the delivery of stimulation of the targetednerve (the Hypoglossal nerve, for example). In the exemplary strategy ofFIG. 9, stimulation is delayed after a patient begins a sleep session,allowing the patient to fall asleep before stimulation begins.Stimulation from each of the functional groups takes turns ramping up,holding the tongue in the desired position for a period of time that issustainable without significant fatigue, before the next group startsand the previous group stops allowing muscle fibers associated with theprevious group to relax, and which helps to prevent fatigue but whichmaintains desirable tongue position all the time.

The remaining effort in programming the two or more electrode contactsis to select electrode contacts and assign them to functional groups.During stimulation, only a single functional group will be on at a timeor on at overlapping out of phase intervals, but a group may containmore than one contact. The effect of having more than one contact shouldadditionally be tested to make sure that the sensation of the twocontacts or groups on at the same time does not result in discomfort forthe patient. Ostensibly, if a single contact results in good airwayopening there is little reason to add another contact to the sametargeted efferent. If the use of two contacts provides better openingthen the pair should be tested together and assigned to the same group.

In certain embodiments, at least two functional groups are defined, sothat the load of maintaining tongue position is shared, prolonging thetime until fatigue sets in or preventing it altogether. Stimulationstarts with the first group, which ramps up in amplitude to a targetamplitude, stays at the target level for a pre-determined amount of timeand then is replaced or overlapped by the next group. This repeatsthrough one or more of the functional groups. The pattern may repeatbeginning with the first functional group, but need not begin with thesame functional group each time. In certain exemplary embodiments, thegroups may be programmed to ramp up in amplitude while the previousgroup is still on and at the target level of the next group the firstgroup would be programmed to terminate. This would maintain a constant,continuous level of stimulation that is shared amongst the programmedgroups. The cycle repeats until the end of the sleep session.

The load of maintaining muscle tone and position is shared by all of thefunctional groups. In one embodiment, each contact is pulsed atdifferent or overlapping intervals (FIGS. 10A and 10B). This prevents orminimizes fatigue by alternately resting and stimulating targeted musclegroups and thereby preventing the tongue from falling into a positionthat can cause apnea or hypopnea. The predetermined amount of time thata group is programmed to stay on may be determined by observing thetongue at a chosen stimulation frequency and determining how long theresulting contraction can be maintained before fatigue causes theresulting position control to degrade.

In another embodiment, each contact is pulsed at a fraction of the totaltarget frequency (discussed below) and out of phase with each of theother contacts (FIG. 10B). For example, if the target frequency is 30pps, each contact is pulsed at 10 pps with the other contactsinterleaved between each pulse rather than pulsing each contact for aninterval at 30 pps as shown in FIG. 9. In such an embodiment, the pulsesare out of phase with one another so each contact pulses sequentially ina nearly continuous pattern to share the stimulation load of thecontacts. Spreading the load over each of the contacts allows a muchlower frequency to be used that allows for near constant musclestimulation without or substantially without fatigue or diminishedpositioning.

Using multiple functional groups, in either a staggered or interleavedconfiguration, allows the tongue to be continuously or near-continuouslystimulated, maintaining the tongue in a desired position even thougheach functional group only stimulates its neural population for aportion of a stimulation cycle. This exemplary method maintainscontinuous or near-continuous stimulation by load sharing betweenmultiple functional groups, with each group—activating one or moredesired tongue muscle. This method has the additional feature that groupramps would occur once for a sleep session and that stimulation levelswould be maintained at their target levels, reducing the complexity ofstimulation control.

Stimulus Ramping

FIGS. 9 and 52 illustrate an exemplary stimulus ramp. In certainexemplary embodiments, a stimulus ramp is used to maximize patientcomfort and/or for prevention of arousal. With a patient who is awake,stimulation producing a noticeable, smooth contraction is important. Intreating a sleeping patient suffering from obstructive sleep apnea,however, achieving the smallest contraction necessary to treat thecondition—thout waking the patient—is important. The contraction onlyneeds to be sufficient to move the tongue forward enough or make airway(the pharyngeal wall) tense/rigid enough to prevent an apnea event fromoccurring, and may not even be visible to the naked eye.

The sensation of the applied electrical pulses to the nerve, and theaccompanying involuntary movement of the tongue generates is, at best,unnatural. In certain exemplary embodiments, the goal is to minimizesensation to a level acceptable to the patient. In certain exemplaryembodiments, stimulus is gradually ramped up to ease the patient up to atarget stimulus level. Stimulus starts at a threshold level, withstimulus magnitude slowly increasing to the target level. As is known tothose skilled in the art, either stimulus magnitude or phase durationmay be modulated to achieve control between the threshold and targetlevels.

If stimulation were immediately applied without a ramp, the stimulationcould awaken or arouse the patient and adversely affect their sleep,just as an apnea event would. The exemplary embodiments of the presentinvention therefore employ the method of amplitude magnitude ramps atthe start of stimulation to address this issue. The duration of thisramp is often several seconds long so that the change is gradual and thepatient is able to adjust to the delivery of stimulation to the tissue.

In certain exemplary embodiments, an amplitude ramp of approximately 5to 10 seconds is selected, (i.e., where stimulus increases to a desiredlevel in 5 to 10 seconds). Stimulation is started at the thresholdamplitude and slowly increased to the target amplitude until significanttongue movement is observed. Significant movement is defined as at leastone movement that decreases airway resistance or results in increasedairway air flow, or which maintains tongue muscle tone. The movement ofthe tongue and its affect on the airway can be observed with anendoscope placed in the nasal cavity, by use of fluoroscopy, or byobserving the front of the oral cavity and the overall position of thetongue. Other ways of observing known to those skilled in the art can beused without departing from the scope of the invention. This is theoperational point or targeted stimulation level that will be used if itis decided that this contact is to be included in the programmedstimulation protocol designed to affect the tongue during the sleepingsession.

Frequency Adjustment

Another factor affecting the perceived comfort for the patient is thefrequency of a pulsatile waveform. Stimulating at a very low frequency,such as approximately 1 to 3 pps, allows the easy identification of anamplitude threshold as distinct twitches or brief contractions of themuscle. These twitches or contractions are readily discernible, andoften can be felt by the patient. Increasing the frequency to asufficiently fast rate results in the fusion of the twitches (referredto as tetanus) and the relaxation between them into a smooth musclecontraction. This also quite often results in a sensation that is morecomfortable for the patient, and is it is generally more comfortable forthe patient as the frequency increases. Above a certain frequency,however, the sensation may again become uncomfortable, possiblyassociated with the level of work associated with the increased numberof muscle contractions. This comfort level must be experimentallydetermined and it can vary from patient to patient. The amplitude isthen increased to the target amplitude to sufficiently position thetongue as described above.

Delayed Stimulation Onset

In certain embodiments, stimulation is delayed until after a patient isasleep. By monitoring a patient in a sleep laboratory and/or byinterviewing a patient's partner, it can be determined how much time isnecessary to delay stimulation onset. In certain embodiments, this delayis programmed into the IPG 1370. When the patient initiates a sleepsession of the device, the IPG 1370 then waits for the programmed delayperiod to complete before applying stimulation to the Hypoglossal nerve.The delay for stimulation onset may also be associated with the point atwhich sleep apnea begins to appear in the sleep cycle of the patient. Ifapneas do not begin to appear until the deepest stage of sleep (rapideye movement or REM) then it may be advantageous to delay the onset ofstimulation well past the point at which the patient begins to sleep anduntil just before the point at which apnea becomes apparent. Thestimulation may then be applied for a predetermined period of timeand/or until the IPG 1370 is deactivated. In one embodiment, the IPG1370 is activated and deactivated via the RCC 2272.

Delaying stimulation onset, using frequency and/or amplitude modulationfor a gradual ramp up or down to a desired stimulation all reduce thechances of arousing the patient in the middle of sleep, making tonicstimulation more likely to succeed. In certain treatment methods,sleeping medication for those patients who may be sensitive to theelectrical stimulation activated movement may increase the chances ofsuccessful treatment.

In an exemplary embodiment, a stimulation amplitude threshold isdetermined by initially setting a low stimulation frequency between 1and 3 pps. A typical waveform such as 200 μs cathodic phase duration, 50μs interphase interval and 800 μs anodic phase duration is selected (theandodic phase amplitude would then be one fourth the amplitude of thecathodic phase amplitude), and then waveform amplitude is slowlyincreased from approximately 0 μA up to a level at which the tonguemuscle can be seen to twitch with each pulse, or when the patient beginsto feel the pulsatile sensation. This is the point at which theelectrical stimulation is just enough to excite fibers within the nervebundle. This setting is noted as the threshold amplitude and stimulationis stopped.

Each contact may be further tested to see what frequency should be usedfor initial stimulation. Experience and literature evidence suggeststhat the higher the frequency, the more comfortable the sensation ofelectrical stimulation is for the patient. The more comfortable thestimulation, the less likely the patient will be awakened. In theseexemplary embodiments, stimulation starts at a frequency above thetarget frequency, and gradually decreases to the preferred targetfrequency. A preferred frequency is a frequency comfortable to thepatient that produces a desired stimulus response. In one embodiment,one or more contacts deliver the target frequency at different intervals(FIGS. 9 and 10A). In another embodiment, the target frequency isgenerally divided by the number of contacts and is spread or interleavedover the contacts (FIG. 10C).

Determining the starting frequency is performed by setting the contactstimulation parameters to those determined for target stimulation andincluding an amplitude ramp, typically 5 to 10 seconds. Stimulation isstarted and the frequency is slowly adjusted upwards, checking with thepatient for comfort. It may be necessary to reduce amplitude with higherfrequency in order to maintain comfort but if so, then the targetfrequency should be checked again at the lower amplitude to verify thatit still produces a functional movement.

Once all of the contacts have been evaluated a common higher frequencyshould be selected which is the lowest of all of the contactfrequencies. The frequency is set to the lowest contact frequency thatachieves a response resulting in increased airway airflow or decreasedairway resistance. Using the lowest frequency increases the time untilfatigue occurs. This frequency is used as the startup frequency to beused after the delay from the beginning of the session has completed.

Exemplary Method of Use

The section below describes an exemplary method of patient use of thesystem. In the method described, the patient uses a remote control andcharger 2272 (RCC) to operate and maintain the system. In thisembodiment, the combination remote control and charger has a mini-USBconnector, which charges an internal battery in the RCC 2272. Optionallythe RCC 2272 may rest in a cradle kept on the patient's nightstand. Thecradle would have spring loaded contacts, which make connection to theRCC 2272 much like a cordless phone to charge the RCC battery. Thecradle may also use a mini-USB connector to attach to a wall mountedpower supply.

To start a sleep session the patient uses the RCC 2272 to activate theimplantable pulse generator (IPG). In certain embodiments, the patientfirst activates the RCC 2272, which then attempts to communicate to theIPG 1370. If the RCC 2272 is unable to communicate with the IPG 1370,the RCC 2272 indicates to the patient (by, for example, beeping threetimes and illuminating an LED) that the RCC 2272 could not communicatewith the IPG 1370. This might mean that the IPG 1370 is so low inbattery power that the IPG 1370 needs to be charged, or that the RCC2272 is not close enough to communicate to the IPG 1370. If the IPG 1370needs charging then the patient would attach a charge coil and cable tothe RCC 2272, place the coil over the IPG 1370, press the charge switchon the RCC 2272 and charge the IPG 1370 until the battery of the IPG1370 has enough energy to stimulate, up to two or three hours for acompletely depleted IPG 1370.

If the IPG 1370 has enough energy to communicate and is in range of theRCC 2272, then the RCC 2272 would acquire the stimulation status andbattery level. Assuming that this is the start of a normal sleep sessionthe IPG 1370 would have been in the “Stimulation Off” state.

The RCC 2272 then reports the battery status by indicating the batteryLED in the green state for full, amber for medium and red for low. Ifthe battery level is full or medium then the IPG 1370 would beinstructed to start a sleep session and the IPG 1370 On/Off LED would beset to green. If the battery were low then the IPG 1370 would beinstructed to stay off and the IPG On/Off LED would be set to red. Thepatient could then charge the IPG 1370 to use for one or more sleepsessions.

Once a sleep session starts, the IPG 1370 initiates a startup delayperiod allowing the patient to fall asleep before stimulation starts. Atthe end of this delay, stimulation starts with the first functionalgroup, ramping amplitude from threshold to target amplitude and thenholding for the remainder of its On-Time duration. In interleaved orstaggered mode, all groups would start simultaneously, utilizing theirindividual ramp up parameters, then maintain stimulation levels at thetarget levels for the duration of the sleep period. At the beginning ofstimulation, the stimulation frequency is set to the startup frequencydetermined during programming. This frequency would be ramped downwardsto the target frequency for a programmed duration after which the targetfrequency is used.

Alternative Embodiments

FIGS. 53 through 62 depict alternative embodiments of the OSA systemthat may be considered as alternatives to the system elements describedabove. FIG. 53 depicts the various elements that could be alternativelyand/or additionally used: a small charger that may or may not have auser interface, a keyfob 5380 that may or may not have a user interface,and a remote control that may take advantage of commercially availabledevices, such as a hand-held computer, smart phone 5382, or similarcommercially available device, which may provide useful wirelessinterfaces and user interfaces for the OSA application.

FIG. 54 depicts a pair of exemplary devices which could act as remotecontrols. On the left is the Apple iPod® Touch 5382 a, and on the rightis a Blackberry® Smartphone 5382 b. Both devices have excellent userinterfaces, have wireless technology support to allow communication tothe various OSA system elements, and are readily available andunderstandable by many of the patients that could use the OSA system.

FIG. 55 depicts a keyfob telemetry relay that could be used to provide acommunication bridge between the remote control and the IPG 1370.Standard wireless technologies, such as Bluetooth® or Wi-Fi could beimplemented within the keyfob relay, along with MICS telemetry forcommunication to the IPG 1370. The keyfob relay need only be withintelemetry range of the IPG 1370 and the remote control, for instance, inthe pocket of the patient. Since the keyfob 5380 may only be required asa relay device, current consumption may be quite low, and the keyfob5380 could run off a small lithium primary coin cell battery that wouldonly need to be changed after rather long periods of time. Since thekeyfob 5380 may only act as a relay, the keyfob 5380 may not need a userinterface (such as a keyboard or LED display) at all, but if desired,either or both of these could be added. Alternatively, the remotecontrol could allow the insertion of a hardware relay function toprovide MICS telemetry directly from the remote control to the IPG.

FIG. 56 depicts an exemplary charger and charger coil. This element mayalso have no user interface such as a keyboard or LED displays, but theycould be added if desired.

FIG. 57 illustrates a potential use model for the alternativeembodiments for use by the clinician in programming or interrogating theOSA system. The aCM could be the same as that described previously, anda wireless interface such as Bluetooth® or Wi-Fi could be used tocommunicate with the charger. The charger could then communicate withthe IPG 1370 using MICS telemetry, or if that were not possible for somereason, then the charger coil (CC) could be used as a backup telemetrychannel. Alternatively, as depicted in FIG. 58, the aCM couldcommunicate through the keyfob relay to the IPG 1370. Using Bluetooth®,Wi-Fi or some other industry standard wireless interface between the aCMand the keyfob 5380, and MICS telemetry between the keyfob relay and theIPG 1370, communication could be provided to program or interrogate theIPG 1370 in the OSA system. Alternatively, the aCM computer could allowthe insertion of a hardware relay function to provide MICS telemetrydirectly from the aCM to the IPG.

FIG. 58 illustrates the use of the iPhone® (or SmartPhone) 5382 as theremote control to perform routine operations in the OSA system. Theremote control would communicate with the keyfob 5380 which would relaythe communication with the IPG 1370 via MICS telemetry.

FIG. 60 illustrates that the charger and telemetry coil could take theplace of the keyfob 5380 by providing MICS telemetry or secondaryinductive link telemetry should the MICS telemetry be non-functional forsome reason.

FIG. 59 illustrates the use of the simplified charger and charger coilfor charging of the IPG 1370. The charger would normally be placed upona cradle or docking station 5378 to re-charge its own internal batterysupply, possibly a lithium polymer battery. A microcontroller inside ofthe charger could detect when the patient removes the charger from itscradle and begin to automatically search for the IPG 1370. Once the IPG1370 is located and it has determined that the charger coil is placedover the IPG 1370 it may then proceed to charge the IPG 1370 asdescribed previously. If the charger did not find the IPG 1370 withinsay five minutes of removal from the cradle or docking station 5378,then if the charger had a membrane switch panel or other user interfaceit could be independently commanded to start or stop the chargingprocess. Again, alternatively, and as depicted in FIG. 62, the remotecontrol could be used to communicate with the charger to start and/orstop the charging process.

It shall be understood that these and many other embodiments of the OSAsystem could be implemented that would provide the OSA treatment,maintain the operation of the OSA system, and provide information to thepatient and clinician for routine use, programming and maintenance ofthe OSA sleep therapy.

It will be appreciated by those skilled in the art that changes could bemade to the exemplary embodiment shown and described above withoutdeparting from the broad inventive concept thereof. It is understood,therefore, that this invention is not limited to the exemplaryembodiment shown and described, but it is intended to covermodifications within the spirit and scope of the present invention asdefined by the claims. For example, “an embodiment,” and the like, maybe inserted at the beginning of every sentence herein where logicallypossible and appropriate such that specific features of the exemplaryembodiment may or may not be part of the claimed invention andcombinations of disclosed embodiments may be combined. Unlessspecifically set forth herein, the terms “a”, “an” and “the” are notlimited to one element but instead should be read as meaning “at leastone”.

Further, to the extent that the method does not rely on the particularorder of steps set forth herein, the particular order of the stepsshould not be construed as limitation on the claims. The claims directedto the method of the present invention should not be limited to theperformance of their steps in the order written, and one skilled in theart can readily appreciate that the steps may be varied and still remainwithin the spirit and scope of the present invention.

I/We claim:
 1. A system used for controlling a position of a patient's tongue, the system comprising: an electrode configured to apply one of at least one electric signal to one of at least one targeted motor efferent located within a Hypoglossal nerve to stimulate at least one muscle of the tongue.
 2. The system of claim 1, further comprising an implantable pulse generator (IPG) coupled to the electrode.
 3. The system of claim 2, further comprising a remote control and charger coupled to the IPG.
 4. The system of claim 3, wherein the remote control powers the IPG.
 5. The system of claim 3, where the remote control re-charges the IPG.
 6. The system of claim 3, further comprising a docking station configured to charge the remote control and charger.
 7. The system of claim 3, wherein the remote control and charger are configured to couple with a computer to program the IPG.
 8. The system of claim 2, wherein the electrode includes a plurality of contacts.
 9. The system of claim 8, wherein the IPG is programmable to assign the contacts to one of a plurality of functional groups.
 10. The system of claim 9, wherein the IPG is programmable to sequence or interleave the functional groups.
 11. The system of claim 9, wherein each functional group maintains an open airway in the patient and a first functional group includes at least one or more different muscles than a second functional group.
 12. The system of claim 2, wherein the IPG is covered by a hermetic enclosure.
 13. The system of claim 2, further comprising a sensor configured to measures the temperature of the IPG.
 14. The system of claim 1, wherein the electrode includes a plurality of contacts.
 15. The system of claim 14, wherein electrode includes six contacts.
 16. The system of claim 14, wherein the contacts are each driven by their own independent current source.
 17. The system of claim 1, further comprising a primary boot loader.
 18. The system of claim 17, further comprising a secondary boot loader.
 19. The system of claim 1, further comprising a Medical Implant Communication Service (MICS) telemetry transceiver.
 20. The system of claim 1, further comprising an inductive link telemetry transceiver.
 21. The system of claim 1, wherein the electrode includes a cuff housing configured to wrap around a portion of the Hypoglossal nerve.
 22. The system of claim 1, wherein the electric signal is applied to the Hypoglossal nerve via an open loop system.
 23. The system of claim 1, wherein the electrode is driven by multiple current sources.
 24. The system of claim 1, further comprising event logging memory.
 25. The system of claim 1, further comprising a multiplexer configured to measure impedance of at least one of an electrode contact and patient tissue. 